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GOVERNMENT OF TAMILNADU, , HIGHER SECONDARY, SECOND YEAR, , COMPUTER SCIENCE, , A publication under Free Textbook Programme of Government of Tamil Nadu, , Department of School Education, Untouchability is Inhuman and a Crime, , Index.indd 1, , 20-02-2019 15:06:40
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Government of Tamil Nadu, First Edition, , -, , 2019, , (Published under New Syllabus), , NOT FOR SALE, , Content Creation, , The wise, possess all, , State Council of Educational, Research and Training, © SCERT 2019, , Printing & Publishing, , Tamil NaduTextbook and Educational, Services Corporation, www.textbooksonline.tn.nic.in, , II, , Index.indd 2, , 20-02-2019 15:06:40
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The tremendous effect of the computer and computing technology is in, shaping the modern society for the betterment of mankind. Human, civilization achieved the highest peak with the development, of computer known as “Internet Era”., , PREFACE, , Python being a high level language is good, for beginners to learn due to its easy syntax, and powerful memory management. For any, internet applications, it is good to learn as python being the, better choice., , The user of this textbook being acquainted with the knowledge of C++ in, std XI will have no difficulty in studying python language. No substantial, knowledge nor experience, is required as the examples illustrated in the, book are easy to follow., , HOW, TO USE, THE BOOK, , This book does not require, prior knowledge in computer, Technology, Each unit comprises of simple, activities and demonstrations which can be done by, the teacher, and also students., , Technical terminologies are listed in glossary for easy understanding, The “ Do you know?” boxes enrich the knowledge of reader with, additional information, Workshops are introduced to solve the exercises using software, applications, QR codes are used to link supporting additional, materials in digital form, , How to get connected to QR Code?, o, , Download the QR code scanner from the google play store/, apple app store into your smartphone, , o, , Open the QR code scanner application, , o, , Once the scanner button in the application is clicked, camera opens, and then bring it closer to the QR code in the textbook., , o, , Once the camera detects the QR code, a URL appears in the screen., Click the URL and go to the content page., III, , Index.indd 3, , 20-02-2019 15:06:40
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Index.indd 5, , |, , PhD – Computer Science, , |, , Graph Theory, , Human Computer Interaction – HCI, , |, , |, | NCC Entry, , |, , |, , Internet of Things, , High Performance Computing., , Natural Language Processing | Networks, Distributed Systems, and Security., , Human Computer Interaction, , Graphics and Visualization, , Data Mining, Databases, and Geographical Information Systems., , State Universities https://www.ugc.ac.in, Tata Institute of Fundamental Research, (TIFR) Mumbai www.tifr.res.in, , IISER Educational Institutions, www.iiseradmission.in, Indian Institute of Technology in, various places (IIT’s) www.iitm.ac.in, , SavithiribaiPhule Pune university,, Pune www.unipune.ac.in, , National Institute of Technology, (NITs) www.nitt.edu, Hyderabad central university,, Hyderabad www.uohyd.ac.in, , Delhi University, Delhi www.du.ac.in, , Bioinformatics and Computational Biology, , Cloud Computing, , National Institute of Science Education and, Research (NISER), www.niser.ac.in, , Architectures, Compiler Optimization, and Embedded Systems., |, , Mumbai University, Mumbai www.mu.ac.in, , Jawaharlal Nehru University (JNU) www.jnu.ac.in, , BITS Pilani, https://www.bits-pilani.ac.in, Chennai Mathematical Institute, (CMI) Chennai www.cmi.ac.in, , Institute of Mathematical Sciences (IMSc), Chennai www.imsc.res.in, , Bhaba Atomic Research centre, (BARC) Mumbai www.barc.gov.in, , Research Institutions in various areas of science, , COMPUTER, , SCIENCE, , Applications Software Developer | Big Data Analysts, Cloud Computing Programmer | College/ University Faculty, Computer Programmer | Computer Teacher, Computer Vocational Instructor | Computer Information Research Scientist, Computer Information Systems Manager | Computer Network Architect, Computer Support Specialist | Computer System Analysts, Data Mining Specialist | Database Administrator, Information Security Analysts | Market Research Analysts, Network & Computer System Administrator | Research Assistant, Systems Software Developer | User Interface Designer | Web Developer, , Computer Related Jobs, , | Women Special Entry Scheme, , Technical Graduate Course –TGC, , Tamil Nadu Public Service Commission, , SSC Tech Entry – Officers Training School, , Union Public Service Examination, , Teacher Recruitment Board, |, , |, |, , Staff Selection Examination, Territorial Army, , |, , SSC NAVY (Pilot/Observer), , | Railway Board Examination, , Defence Service Staff College, Nilgiris, , Indian Military Academy, , Judge Advocate General Department-JAG, , Indian Defence Services, , Combined Defence Services –CDS, , Airforce Common Admission Test – AFCAT | Army Education Officer Entry- AEC, , Competitive Exams for Govt. Jobs, , Central Universities www.ugc.ac.in, , Topics for Research after PG in Computer Studies, T, , Towards More Practical Reinforcement Learning,, with Applications to Educational Games, , The Security and Privacy of Web and Mobile Advertising, , Reproducible measurements of web security and privacy, , New Algorithmic Tools for Distributed Similarity Search, , Manipulators And Manipulation In High Dimensional Spaces, , Learning Robust Tractable Models for Vision, , Intelligent Crowdsourcing for Natural Language, Learning and Other AI Applications, , In-situ Semantic 3D Modeling, , Increasing Access to Computer Science for Blind Students, , Improving Fault Tolerance and Performance of Data Center Networks, , |, , Game Theory |, , Graphics and Visualization, , Embedded Systems, , Digital Pathology: Diagnostic Errors,, Viewing Behavior and Image Characteristics, , Designing and Evaluating Information Gathering Robots, , Comprehensive analysis of RNA sequencing experiments, , Capturing and Visualizing Persona Through Faces, , BioInformatics and Computational Biology, , Following are the latest topics for PhD in computer science:, , MPhil –Computer Science, , After PG courses, A, , CAREER GUIDANCE, , V, , 20-02-2019 15:06:41
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Table of Contents, Computer Science-II Year, UNIT No., , Chapter, , Page., No, 1, , Title, , 1, , Function, , 2, , Data Abstraction, , 11, , 3, , Scoping, , 21, , 4, , Algorithmic Strategies, , 31, , 5, , Python -Variables and Operators, , 47, , 6, , Control Structures, , 67, , 7, , Python functions, , 89, , 8, , Strings and String manipulations, , 114, , 9, , Lists, Tuples, Sets and Dictionary, , 132, , 10, , Python Classes and objects, , 170, , UNIT-IV, Database, concepts and, MySql, , 11, , Database Concepts, , 189, , 12, , Structured Query Language (SQL), , 205, , 13, , Python and CSV files, , 232, , UNIT-V, Integrating, Python with, MySql and C++, , 14, , Importing C++ programs in Python., , 267, , 15, , Data manipulation through SQL, , 291, , 16, , Data visualization using pyplot: line chart, pie, chart and bar chart, , 320, , UNIT- I, Problem, Solving, Techniques, UNIT- II, Core Python, UNIT-III, Modularity, and OOPS, , Glossary, , 335, , Annexure-1, , List of Python functions, , 341, , Annexure-2, , Installation of MySQL and Creating a Database, , 345, , Annexure-3, , Installation of MinGW, , 346, , Annexure-4, , Installation of pip, , 351, , E - book, , Assessment, , DIGI links, , VI, , Index.indd 6, , 20-02-2019 15:06:41
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Unit, , I, , CHAPTER 1, FUNCTION, , 1.2 Function with respect to, Programming language, , Learning Objectives, After the completion of this chapter, the, student will be able to:, , • Interface Vs Implementation., , A function is a unit of code that is, often defined within a greater code structure., Specifically, a function contains a set of, code that works on many kinds of inputs,, like variants, expressions and produces a, concrete output., , • Pure functions., , 1.2.1 Function Specification, , • Side - effects (impure functions)., , Let us consider the example a:= (24)., a:= (24) has an expression in it but (24), is not itself an expression. Rather, it is a, function definition. Definitions bind values, to names, in this case the value 24 being, bound to the name ‘a’. Definitions are not, expressions, at the same time expressions are, also not treated as definitions. Definitions, are distinct syntactic blocks. Definitions can, have expressions nested inside them, and, vice-versa., , • Understand Function Specification., • Parameters (and arguments)., , 1.1 Introduction, The most important criteria in, writing and evaluating the algorithm is the, time it takes to complete a task. To have, a meaningful comparison of algorithms,, the duration of computation time must be, independent of the programming language,, compiler, and computer used. As you, aware that algorithms are expressed using, statements of a programming language. If a, bulk of statements to be repeated for many, numbers of times then subroutines are used, to finish the task., , 1.2.2 Parameters (and arguments), Parameters are the variables in a, function definition and arguments are, the values which are passed to a function, definition., , Subroutines are the basic building, blocks of computer programs. Subroutines, are small sections of code that are used to, perform a particular task that can be used, repeatedly. In Programming languages these, subroutines are called as Functions., , 1. Parameter without Type, Let us see an example of a function, definition:, , 1, , Chapter 1.indd 1, , 20-02-2019 15:17:15
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mandatory. Generally we can leave out, these annotations, because it's simpler to, let the compiler infer them. There are times, we may want to explicitly write down types., This is useful on times when you get a type, error from the compiler that doesn't make, sense. Explicitly annotating the types can, help with debugging such an error message., , (requires: b>=0 ), (returns: a to the power of b), let rec pow a b:=, if b=0 then 1, else a * pow a (b-1), In the above function definition, variable ‘b’ is the parameter and the value, which is passed to the variable ‘b’ is the, argument. The precondition (requires) and, postcondition (returns) of the function, is given. Note we have not mentioned any, types: (data types). Some language compiler, solves this type (data type) inference, problem algorithmically, but some require, the type to be mentioned., , The syntax to define functions is close, to the mathematical usage: the definition is, introduced by the keyword let, followed by, the name of the function and its arguments;, then the formula that computes the image, of the argument is written after an = sign. If, you want to define a recursive function: use, “let rec” instead of “let”., Syntax: The syntax for function definitions:, , In the above function definition if, expression can return 1 in the then branch,, by the typing rule the entire if expression, has type int. Since the if expression has, type ‘int’, the function's return type also be, ‘int’. ‘b’ is compared to 0 with the equality, operator, so ‘b’ is also a type of ‘int’. Since ‘a’, is multiplied with another expression using, the * operator, ‘a’ must be an int., , let rec fna1 a2 ... an := k, Here the ‘fn’ is a variable indicating, an identifier being used as a function, name. The names ‘a1’ to ‘an’ are variables, indicating the identifiers used as parameters., The keyword ‘rec’ is required if ‘fn’ is to be, a recursive function; otherwise it may be, omitted., , 2. Parameter with Type, Now let us write the same function, definition with types for some reason:, , Note, A function definition which call, itself is called recursive function., , (requires: b> 0 ), (returns: a to the power of b ), let rec pow (a: int) (b: int) : int :=, , For example: let us see an example to check, whether the entered number is even or odd., , if b=0 then 1, else a * pow b (a-1), When we write the type annotations, for ‘a’ and ‘b’ the parentheses are, XII Std Computer Science, , Chapter 1.indd 2, , 2, , 20-02-2019 15:17:15
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interface. In our example, anything that, "ACTS LIKE" a light, should have function, definitions like turn_on () and a turn_off, (). The purpose of interfaces is to allow the, computer to enforce the properties of the, class of TYPE T (whatever the interface is), must have functions called X, Y, Z, etc., , (requires: x>= 0), let rec even x :=, x=0 || odd (x-1), return ‘even’, (requires: x>= 0), let odd x :=, x<>0 && even (x-1), return ‘odd’, , A class declaration combines the, external interface (its local state) with an, implementation of that interface (the code, that carries out the behaviour). An object is, an instance created from the class., , The syntax for function types:, x→y, x1 → x2 → y, x1 → ... → xn → y, , The interface defines an object’s visibility to, the outside world., , The ‘x’ and ‘y’ are variables indicating, types. The type x → y is the type of a function, that gets an input of type ‘x’ and returns an, output of type ‘y’. Whereas x1 → x2 → y is, a type of a function that takes two inputs,, the first input is of type ‘x1’ and the second, input of type ‘x2’, and returns an output of, type ‘y’. Likewise x1 → … → xn → y has, type ‘x’ as input of n arguments and ‘y’ type, as output., , The difference between interface and, implementation is, Interface, Interface just, defines what, an object can, do, but won’t, actually do it, , Implementation, carries out the, instructions defined, in the interface, , Note, All functions are static, definitions. There is no dynamic, function definitions., , In object oriented programs classes are, the interface and how the object is processed, and executed is the implementation., , 1.3 Interface Vs Implementation, , • The class template specifies the interfaces, to enable an object to be created and, operated properly., , 1.3.1 Characteristics of interface, , An interface is a set of action that an, object can do. For example when you press, a light switch, the light goes on, you may, not have cared how it splashed the light. In, Object Oriented Programming language,, an Interface is a description of all functions, that a class must have in order to be a new, , • An object's attributes and behaviour is, controlled by sending functions to the, object., For example, let's take the example of, increasing a car’s speed., 3, , Chapter 1.indd 3, , Implementation, , Function, , 20-02-2019 15:17:15
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let min 3 x y z :=, if x < y then, , if x < z then x else z, else, , if y < z then y else z, , ENGINE, , getSpeed, , 1.4 Pure functions, required, speed, , No, , Pure functions are functions which, will give exact result when the same, arguments are passed. For example the, mathematical function sin (0) always results, 0. This means that every time you call the, function with the same arguments, you will, always get the same result. A function can, be a pure function provided it should not, have any external variable which will alter, the behaviour of that variable., , Pull Fuel, , Yes, , Return, , The person who drives the car, doesn't care about the internal working. To, increase the speed of the car he just presses, the accelerator to get the desired behaviour., Here the accelerator is the interface between, the driver (the calling / invoking object) and, the engine (the called object)., , Let us see an example, let square x, return: x * x, , In this case, the function call would, be Speed (70): This is the interface., , The above function square is a pure, function because it will not give different, results for same input., , Internally, the engine of the car is, doing all the things. It's where fuel, air,, pressure, and electricity come together to, create the power to move the vehicle. All of, these actions are separated from the driver,, who just wants to go faster. Thus we separate, interface from implementation., , There are various theoretical, advantages of having pure functions. One, advantage is that if a function is pure, then, if it is called several times with the same, arguments, the compiler only needs to, actually call the function once. Lt’s see an, example, , Let us see a simple example, consider, the following implementation of a function, that finds the minimum of its three, arguments:, , let i: = 0;, if i <strlen (s) then, , , -- Do something which doesn't affect s, ++i, , XII Std Computer Science, , Chapter 1.indd 4, , 4, , 20-02-2019 15:17:15
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If it is compiled, strlen (s) is called, each time and strlen needs to iterate over, the whole of ‘s’. If the compiler is smart, enough to work out that strlen is a pure, function and that ‘s’ is not updated in the, loop, then it can remove the redundant, extra calls to strlen and make the loop to, execute only one time. From these what we, can understand, strlen is a pure function, because the function takes one variable as a, parameter, and accesses it to find its length., This function reads external memory but, does not change it, and the value returned, derives from the external memory accessed., , Here the function Random is impure, as it is not sure what will be the result when, we call the function., 1.4.2 Side-effects (Impure functions), As you are aware function has side, effects when it has observable interaction, with the outside world. There are situations, our functions can become impure though, our goal is to make our functions pure., Just to clarify remember that side effect is, not a necessary bad thing.Sometimes they, are useful (especially outside functional, programming paradigm)., Modify variable outside a function, , Note, Evaluation, of, pure, functions does not cause any side, effects to its output, , One of the most popular groups of, side effects is modifying the variable outside, of function., For example, let y: = 0, (int) inc (int) x, y: = y + x;, return (y), , 1.4.1 Impure functions, The variables used inside the, function may cause side effects though the, functions which are not passed with any, arguments. In such cases the function is, called impure function. When a function, depends on variables or functions outside, of its definition block, you can never be, sure that the function will behave the same, every time it’s called. For example the, mathematical function random() will give, different outputs for the same function call., , In the above example the value of y, get changed inside the function definition, due to which the result will change each, time. The side effect of the inc () function is, it is changing the data of the external visible, variable ‘y’. As you can see some side effects, are quite easy to spot and some of them may, tricky. A good sign that our function impure, (has side effect) is that it doesn’t take any, arguments and it doesn’t return any value., , let Random number, let a := random(), if a > 10 then, , From all these examples and, definitions what we can understand about, the main differences between pure and, impure functions are, , return: a, else, return: 10, 5, , Chapter 1.indd 5, , Function, , 20-02-2019 15:17:15
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Pure Function, , Impure Function, , The return value of, the pure functions, solely, depends, on its arguments, passed. Hence, if, you call the pure, functions, with, the same set of, arguments,, you, will always get, the same return, values., They do not have, any side effects., , The return value, of the impure, functions, does, not solely depend, on its arguments, passed., Hence,, if you call the, impure functions, with the same, set of arguments,, you might get, the, different, return, values, For, example,, random(), Date()., , They, do, not, modify, the, arguments which, are passed to them, , They may modify, the, arguments, which are passed, to them, , 1.4.3 Chameleons of, problem using function, , Recall the In the Chameleons of, Chromeland problem what you have studied, in class XI. suppose two types of chameleons, are equal in number. Construct an algorithm, that arranges meetings between these two, types so that they change their color to the, third type. In the end, all should display the, same color., Let us represent the number of, chameleons of each type by variables a, b, and c, and their initial values by A, B and C,, respectively. Let a = b be the input property., The input – output relation is a =, b = 0 and c = A + B + C. Let us name the, algorithm monochromatize. The algorithm, can be specified as, monochromatize (a, b, c), , Now let’s see the example of a pure, function to determine the greatest common, divisor (gcd) of two positive integer numbers., let rec gcd a b :=, if b <> 0 then gcd b (a mod b) else return a;;, , In the above example program ‘gcd’ is, the name of the function which recursively, called till the variable ‘b’ becomes ‘0’., Remember b and (a mod b) are two, arguments passed to ‘a’ and ‘b’ of the gcd, function., , Chapter 1.indd 6, , -- inputs, , : a = A, b = B, c = C, a = b, , -- outputs, , :, , a = b = 0, c = A+B+C, , In each iterative step, two chameleons, of the two types (equal in number) meet and, change their colors to the third one. For, example, if A, B, C = 4, 4, 6, then the series, of meeting will result in, , output, gcd 13 27;;, - : int = 1, gcd 20536 7826;;, - : int = 2, , XII Std Computer Science, , Chromeland, , iteration, , a, , b, , c, , 0, , 4, , 4, , 4, , 1, , 3, , 3, , 8, , 2, , 2, , 2, , 10, , 3, , 1, , 1, , 12, , 4, , 0, , 0, , 14, , 6, , 20-02-2019 15:17:15
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In each meeting, a and b each, decreases by 1, and c increases by 2. The, solution can be expressed as an iterative, algorithm., , a, b, c, a = b, a = A, b = B, c = C, , a>0, , monochromatize (a, b, c), -- inputs : a = A, b=B, c=C, a=b, -- outputs : a = b = 0, c = A+B+C, while a>0, a, b, c := a-1, b-1, c+2, , True, , a, b, c := a - 1, b - 1, c+2, , False, a = b = 0, c = A + B + C, a, b, c, , Now let us write this algorithm using, function, , The algorithm is depicted in the flowchart, as below, , let rec monochromatize a b c :=, if a > 0 then, a, b, c := a-1, b-1, c+2, else, a:=0, b:=0, c:= a + b + c, return c, , Points to remember:, • Algorithms are expressed using statements of a programming language, • Subroutines are small sections of code that are used to perform a particular task that, can be used repeatedly, • A function is a unit of code that is often defined within a greater code structure, • A function contains a set of code that works on many kinds of inputs and produces a, concrete output, • Definitions are distinct syntactic blocks, • Parameters are the variables in a function definition and arguments are the values, which are passed to a function definition through the function definition., • When you write the type annotations the parentheses are mandatory in the function, definition, • An interface is a set of action that an object can do, • Interface just defines what an object can do, but won’t actually do it, • Implementation carries out the instructions defined in the interface, • Pure functions are functions which will give exact result when the same arguments, are passed, • The variables used inside the function may cause side effects though the functions, which are not passed with any arguments. In such cases the function is called impure, function, , 7, , Chapter 1.indd 7, , Function, , 20-02-2019 15:17:15
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Hands on Practice, 1. Write algorithmic function definition to find the minimum among 3 numbers., 2. Write algorithmic recursive function definition to find the sum of n natural numbers., , Evaluation, Part - I, Choose the best answer, , (1 Mark), , 1. The small sections of code that are used to perform a particular task is called, (A) Subroutines, 2., , (B) Files, , (C) Pseudo code, , (D) Modules, , Which of the following is a unit of code that is often defined within a greater code, structure?, (A) Subroutines, , (B) Function, , (C) Files, , (D) Modules, , 3. Which of the following is a distinct syntactic block?, (A) Subroutines, 4., , (B) Function, , (C) Definition, , (D) Modules, , The variables in a function definition are called as, (A) Subroutines, , (B) Function, , (C) Definition, , (D) Parameters, , 5. The values which are passed to a function definition are called, (A) Arguments, 6., , (B) Subroutines, , (C) Function, , (D) Definition, , Which of the following are mandatory to write the type annotations in the function, definition?, (A) Curly braces, , (B) Parentheses, , (C) Square brackets, , (D) indentations, , 7. Which of the following defines what an object can do?, (A) Operating System, , (B) Compiler (C) Interface, , (D) Interpreter, , 8. Which of the following carries out the instructions defined in the interface?, (A) Operating System, , (B) Compiler (C) Implementation (D) Interpreter, , 9. The functions which will give exact result when same arguments are passed are called, (A) Impure functions, , (B) Partial Functions, , (C) Dynamic Functions, , (D) Pure functions, , XII Std Computer Science, , Chapter 1.indd 8, , 8, , 20-02-2019 15:17:15
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10. The functions which cause side effects to the arguments passed are called, (A) impure function, , (B) Partial Functions, , (C) Dynamic Functions, , (D) Pure functions, Part - II, , Answer the following questions, , (2 Marks), , 1. What is a subroutine?, 2. Define Function with respect to Programming language., 3. Write the inference you get from X:=(78)., 4. Differentiate interface and implementation., 5., , Which of the following is a normal function definition and which is recursive function, definition, , i) let rec sum x y:, , , return x + y, , ii) let disp :, , , print ‘welcome’, , iii) let rec sum num:, , , if (num!=0) then return num + sum (num-1), , else, , , return num, Part - III, , Answer the following questions, , (3 Marks), , 1. Mention the characteristics of Interface., 2. Why strlen is called pure function?, 3. What is the side effect of impure function. Give example., 4. Differentiate pure and impure function., 5. Wha happens if you modify a variable outside the function? Give an example., , 9, , Chapter 1.indd 9, , Function, , 20-02-2019 15:17:15
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Part - IV, Answer the following questions, , (5Marks), , 1. What are called Parameters and write a note on, (i) Parameter without Type, , (ii) Parameter with Type, , 2. Identify in the following program, let rec gcd a b :=, if b <> 0 then gcd b (a mod b) else return a, i) Name of the function, ii) Identify the statement which tells it is a recursive function, iii) Name of the argument variable, iv) Statement which invoke the function recursively, v) Statement which terminates the recursion, 3. Explain with example Pure and impure functions., 4. Explain with an example interface and implementation., REFERENCES, 1., , Data Structures and Algorithms in Python By Michael T.Goodrich, RobertoTamassia and, Michael H. Goldwasser., , 2., , Data Structure and Algorithmic Thinking in Python By Narasimha Karumanchi, , 3., , https://www.python.org, , XII Std Computer Science, , Chapter 1.indd 10, , 10, , 20-02-2019 15:17:16
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Unit, , I, , CHAPTER 2, DATA ABSTRACTION, , 2.2 Abstract Data Types, , Learning Objectives, , Abstract Data type (ADT) is a type (or, class) for objects whose behavior is defined, by a set of value and a set of operations., , After the completion of this chapter, the, student will be able to Understand, • what is Abstract Data structures., , The definition of ADT only mentions, what operations are to be performed but not, how these operations will be implemented. It, does not specify how data will be organized, in memory and what algorithms will be, used for implementing the operations., It is called “abstract” because it gives an, implementation independent view. The, process of providing only the essentials and, hiding the details is known as abstraction., , • Abstract data type., • Difference between concrete and abstract, implementation., • Pairs., • Data Abstration in Structure., , 2.1, , Data AbstractionIntroduction, , Data abstraction is a powerful, concept in computer science that allows, programmers to treat code as objects — for, example, car objects, pencil objects, people, objects, etc. Programmers need not to worry, about how code is implemented — they have, to just know what it does., , You can see that these definitions, do not specify how these ADTs will be, represented and how the operations will be, carried out. There can be different ways to, implement an ADT, for example, the List, ADT can be implemented using singly linked, list or doubly linked list. Similarly, stack, ADT and Queue ADT can be implemented, using lists., , This is especially important when, several people are doing a project. Here, project refers to the programming .With, data abstraction, your group members won’t, have to read through every line of your code, to understand. They can just assume that it, does work., , Data abstraction replicate how we, think about the world. For example, when, you want to drive a car, you don’t need to, know how the engine was built or what, kind of material the tires are made of. You, just have to know how to turn the wheel, and press the gas pedal. To facilitate data, abstraction, you will need to create two, types of functions: constructors, and, selectors., , Abstraction provides modularity, (modularity means splitting a program in, to many modules). Classes (structures) are, the representation for “Abstract Data Types”,, (ADT), 11, , Chapter 2.indd 11, , 20-02-2019 15:18:04
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Notice that you don’t need to know, how these functions were implemented. You, are assuming that someone else has defined, them for us., , 2.3 constructors and selectors, Constructors are functions that, build the abstract data type. Selectors are, functions that retrieve information from, the data type., , It’s okay if the end user doesn’t know, how functions were implemented. However,, the functions still have to be defined by, someone., , For example, say you have an abstract, data type called city. This city object will, hold the city’s name, and its latitude and, longitude. To create a city object, you’d use a, function like, , Let us identify the constructors and, selectors in the above code, As you already know that, Constructors are functions that build the, abstract data type. In the above pseudo code, the function which creates the object of the, city is the constructor., , city = makecity (name, lat, lon), To extract the information of a city, object, you would use functions like, • getname(city), , city = makecity (name, lat, lon), , • getlat(city), , Here makecity (name, lat, lon) is the, constructor which creates the object city., , • getlon(city), The following pseudo code will, compute the distance between two city, objects:, , (name, lat, lon), , make city ( ), , distance(city1, city2):, lt1, lg1 := getlat(city1), getlon(city1), , city, , lt2, lg2 := getlat(city2), getlon(city2), return ((lt1 - lt2)**2 + (lg1 - lg2)**2))1/2, , lat, , Selectors are nothing but the, functions that retrieve information from the, data type. Therefore in the above code, , lt1, lg1 := getlat(city1), getlon(city1), , • getname(city), , is read as lt1 becomes the value of, getlat(city1) and lg1 becomes the value of, getlont(city1)., , Chapter 2.indd 12, , lon, , Fig 1 constructor, , In the above code read distance(),, getlat() and getlon() as functions and read, lt as latitude and lg longitude. Read := as, “assigned as” or “becomes”, , XII Std Computer Science, , value passed as parameter, , • getlat(city), • getlon(city), are the selectors because these functions, extract the information of the city object, 12, , 20-02-2019 15:18:04
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city, , value passed as parameter city, , getname ( ), , value passed as parameter, , value passed as parameter, , getlon ( ), , getlat ( ), , Now let us consider one more example to, identify the constructor and selector for a, slope.Read - - as comments., , representation is defined as an independent, part of the program., Note, In concrete data representation, a, definition for each function is known, , - - constructor, makepoint(x, y):, return x, y, - - selector, xcoord(point):, return point[0], - -selector, ycoord(point):, return point[1], , Any program consist of two parts., The two parts of a program are, the part, that operates on abstract data and the part, that defines a concrete representation, is, connected by a small set of functions that, implement abstract data in terms of the, concrete representation. To illustrate this, technique, let us consider an example to, design a set of functions for manipulating, rational numbers., , Note, Data abstraction is supported by, defining an abstract data type (ADT),, which is a collection of constructors, and selectors. Constructors create an, object, bundling together different pieces, of information, while selectors extract, individual pieces of information from the, object., , Example, A rational number is a ratio of, integers, and rational numbers constitute, an important sub-class of real numbers., A rational number such as 8/3 or 19/23 is, typically written as:, , 2.4 Representation of Abstract, datatype using Rational, numbers, , <numerator>/<denominator>, where both the <numerator> and, <denominator> are placeholders for integer, values. Both parts are needed to exactly, characterize the value of the rational number., Actually dividing integers produces a float, approximation, losing the exact precision of, integers., , The basic idea of data abstraction is, to structure programs so that they operate, on abstract data. That is, our programs, should use data in such a way, as to make, as few assumptions about the data as, possible. At the same time, a concrete data, 13, , Chapter 2.indd 13, , city, , Data Abstraction, , 20-02-2019 15:18:04
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8/3 =2.6666666666666665, , component. Let us further assume that the, constructor and selectors are also available., , However, you can create an exact, representation for rational numbers by, combining together the numerator and, denominator., , We are using here a powerful strategy, for designing programs: 'wishful thinking'., We haven't yet said how a rational number, is represented, or how the constructor and, selectors should be implemented., , As we know from using functional, abstractions, we can start programming, productively before you have an, implementation of some parts of our, program. Let us begin by assuming that, you already have a way of constructing a, rational number from a numerator and a, denominator. You also assume that, given, a rational number, you have a way of, selecting its numerator and its denominator, , Note, Wishful Thinking is the formation, of beliefs and making decisions according, to what might be pleasing to imagine, instead of by appealing to reality., , Example: An ADT for rational numbers, - - constructor, - - constructs a rational number with numerator n, denominator d, rational(n, d), - - selector, numer(x) → returns the numerator of rational number x, denom(y) → returns the denominator of rational number y, Now you have the operations on, rational numbers defined in terms of the, selector functions numer and denom, and, the constructor function rational, but you, haven't yet defined these functions. What, you need is some way to glue together, a numerator and a denominator into a, compound value., , 2.5, , To enable us to implement the, concrete level of our data abstraction, Some, languages like Python provides a compound, structure called Pair which is made up of list, or Tuple. The first way to implement pairs is, with the List construct., , The pseudo code for the, representation of the rational number using, the above constructor and selector is, , 2.5.1 List, List is constructed by placing, expressions within square brackets, separated by commas. Such an expression, is called a list literal. List can store multiple, values. Each value can be of any type and, can even be another list., , x,y:=8,3, rational(n,d), numer(x)/numer(y), - - output : 2.6666666666666665, XII Std Computer Science, , Chapter 2.indd 14, , Lists,Tuples, , 14, , 20-02-2019 15:18:04
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Example for List is [10, 20]., , code : a numerator and a denominator., , The elements of a list can be accessed, in two ways. The first way is via our familiar, method of multiple assignment, which, unpacks a list into its elements and binds, each element to a different name., , rational(n, d):, , return [n, d], , numer(x):, , return x[0], denom(x):, , lst := [10, 20], , return x[1], , x, y := lst, 2.5.2 Tuple, , In the above example x will become10, and y will become 20., , Remember, a pair is a compound, data type that holds two other pieces of data., So far,we have provided you with two ways, of representing the pair data type. The first, way is using List construct and the second, way to implement pairs is with the tuple, construct., , A second method for accessing the, elements in a list is by the element selection, operator, also expressed using square, brackets. Unlike a list literal, a squarebrackets expression directly following, another expression does not evaluate to a, list value, but instead selects an element, from the value of the preceding expression., , A tuple is a comma-separated, sequence of values, surrounded with, parentheses. Tuple is similar to a list. The, difference between the two is that you, cannot change the elements of a tuple once, it is assigned whereas in a list, elements can, be changed., , lst[0], 10, lst[1], 20, In both the example mentioned above, mathematically we can represent list similar, to a set., , Example colour= ('red', 'blue', 'Green'), Representation of Tuple as a Pair, , lst[(0, 10), (1, 20)] - where, (0, 10), , nums := (1, 2), nums[0], 1, nums[1], 2, , (1, 20), , Index position value Index position value, , Any way of bundling two values, together into one can be considered as a, pair. Lists are a common method to do so., Therefore List can be called as Pairs., , Note the square bracket notation is, used to access the data you stored in the, pair. The data is zero indexed, meaning you, access the first element with nums[0] and, the second with nums[1]., , Representing Rational Numbers Using, List, You can now represent a rational, number as a pair of two integers in pseudo, 15, , Chapter 2.indd 15, , Data Abstraction, , 20-02-2019 15:18:04
Page 22 : person=['Padmashri', 'Baskar', '994222-1234', '
[email protected]'], , 2.6 Data Abstraction in, Structure, , but such a representation doesn't explicitly, specify what each part represents., , As you already know that List allow, data abstraction in that you can give a name, to a set of memory cells. For instance, in the, game Mastermind, you must keep track of, a list of four colors that the player guesses., Instead of using four separate variables, (color1, color2, color3, and color4) you can, use a single variable ‘Predict’, e.g.,, , For this problem instead of using a, list, you can use the structure construct (In, OOP languages it's called class construct), to represent multi-part objects where each, part is named (given a name). Consider the, following pseudo code:, , Predict =['red', 'blue', 'green', 'green'], , class Person:, , What lists do not allow us to do, is name the various parts of a multi- item, object. In the case of a Predict, you don't, really need to name the parts:, , creation( ), firstName := " ", lastName := " ", id := " ", , using an index to get to each color suffices., , email := " ", , But in the case of something more, complex, like a person, we have a multiitem object where each 'item' is a named, thing: the firstName, the, , The new data type Person is pictorially, represented as, , lastName, the id, and the email. One could, use a list to represent a person:, Person, creation ( ), , first Name, last Name, id, email, , XII Std Computer Science, , Chapter 2.indd 16, , class name (multi part data representation), function belonging to the new datatype, , }, , variable (field) beloging to the new, datatype, , 16, , 20-02-2019 15:18:04
Page 23 : Let main() contains, p1:=Person(), , statement creates the object., , firstName := " Padmashri ", , setting a field called firstName with value Padmashri, , lastName :="Baskar", , setting a field called lastName with value Baskar, , id :="994-222-1234", , setting a field called id value 994-222-1234, , email="
[email protected]" setting a field called email with value
[email protected], - - output of firstName : Padmashri, The class (structure) construct, defines the form for multi-part objects that, represent a person. Its definition adds a new, data type, in this case a type named Person., Once defined, we can create new variables, (instances) of the type. In this example, Person is referred to as a class or a type,, while p1 is referred to as an object or an, instance. You can think of class Person as a, cookie cutter, and p1 as a particular cookie., Using the cookie cutter you can make many, cookies. Same way using class you can create, many objects of that type., , So far, you've seen how a class defines, a data abstraction by grouping related data, items. A class is not just data, it has functions, defined within it. We say such functions are, subordinate to the class because their job is, to do things with the data of the class, e.g.,, to modify or analyze the data of a Person, object., Therefore we can define a class as, bundled data and the functions that work, on that data. From All the above example, and explanation one can conclude the, beauty of data abstraction is that we can, treat complex data in a very simple way., , Points to remember:, • Abstract Data type (ADT) is a type (or class) for objects whose behavior is defined by, a set of value and a set of operations., • The definition of ADT only mentions what operations are to be performed but not, how these operations will be implemented., • ADT does not specify how data will be organized in memory and what algorithms, will be used for implementing the operations, • Constructors are functions that build the abstract data type., • Selectors are functions that retrieve information from the data type., • Concrete data types or structures (CDT's) are direct implementations of a relatively, simple concept., • Abstract Data Types (ADT's) offer a high level view (and use) of a concept independent, of its implementation., , 17, , Chapter 2.indd 17, , Data Abstraction, , 20-02-2019 15:18:04
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Points to remember:, • A concrete data type is a data type whose representation is known and in abstract data, type the representation of a data type is unknown, • Pair is a compound structure which is made up of list or Tuple, • List is constructed by placing expressions within square brackets separated by commas, • The elements of a list can be accessed in two ways. The first way is via multiple, assignment and the second method is by the element selection operator, • Bundling two values together into one can be considered as a pair, • List does not allow to name the various parts of a multi-item object., , Evaluation, Part - I, Choose the best answer, , (1 Mark), , 1. Which of the following functions that build the abstract data type ?, (A) Constructors, , (B) Destructors, , (C) recursive, , (D)Nested, , 2. Which of the following functions that retrieve information from the data type?, (A) Constructors, , (B) Selectors, , (C) recursive, , (D)Nested, , 3. The data structure which is a mutable ordered sequence of elements is called, (A) Built in, , (B) List, , (C) Tuple, , (D) Derived data, , (C) Tuple, , (D) Derived data, , 4. A sequence of immutable objects is called, (A) Built in, , (B) List, , 5. The data type whose representation is known are called, (A) Built in datatype, , (B) Derived datatype, , (C) Concrete datatype, , (D) Abstract datatype, , 6. The data type whose representation is unknown are called, (A) Built in datatype, , (B) Derived datatype, , (C) Concrete datatype, , (D) Abstract datatype, , 7. Which of the following is a compound structure?, (A) Pair, XII Std Computer Science, , Chapter 2.indd 18, , (B) Triplet, , (C) single, , (D) quadrat, , 18, , 20-02-2019 15:18:04
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8. Bundling two values together into one can be considered as, (A) Pair, , (B) Triplet, , (C) single, , (D) quadrat, , 9. Which of the following allow to name the various parts of a multi-item object?, (A) Tuples, , (B) Lists, , (C) Classes, , (D) quadrats, , 10. Which of the following is constructed by placing expressions within square brackets?, (A) Tuples, , (B) Lists, , (C) Classes, , (D) quadrats, , Part - II, Answer the following questions, , (2 Marks), , 1. What is abstract data type?, 2. Differentiate constructors and selectors., 3. What is a Pair? Give an example., 4. What is a List? Give an example., 5. What is a Tuple? Give an example., Part - III, Answer the following questions, , (3 Marks), , 1. Differentiate Concrete data type and abstract datatype., 2. Which strategy is used for program designing? Define that Strategy., 3. Identify Which of the following are constructors and selectors?, (a) N1=number(), , (b) accetnum(n1), , (c) displaynum(n1), , (d) eval(a/b), , (e) x,y= makeslope (m), makeslope(n), , (f) display(), 4. What are the different ways to access the elements of a list. Give example., 5. Identify Which of the following are List, Tuple and class ?, (a) arr [1, 2, 34], , (b) arr (1, 2, 34), , (c) student [rno, name, mark], , (d) day= (‘sun’, ‘mon’, ‘tue’, ‘wed’), , (e) x= [2, 5, 6.5, [5, 6], 8.2], , (f) employee [eno, ename, esal, eaddress], , 19, , Chapter 2.indd 19, , Data Abstraction, , 20-02-2019 15:18:04
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Part - IV, Answer the following questions, , (5Marks), , 1. How will you facilitate data abstraction. Explain it with suitable example, 2. What is a List? Why List can be called as Pairs. Explain with suitable example, 3. How will you access the multi-item. Explain with example., , Reference Books, 1. Data structure and algorithmic thinking with python by narasimha karumanchi, 2. sign and analysis of algorithms by s sridhar, 3. Data Structures and Algorithms in Python by Goodrich, Tamassia & Goldwasser, 4. https://www.tutorialspoint.com, , XII Std Computer Science, , Chapter 2.indd 20, , 20, , 20-02-2019 15:18:04
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Unit, , I, , CHAPTER 3, SCOPING, , you assign a variable with := to an instance, (object), you're binding (or mapping) the, variable to that instance. Multiple variables, can be mapped to the same instance., , Learning Objectives, After the completion of this chapter, the, student will be able to, , Note, The process of binding a, variable name with an object is called, mapping. = (equal to sign) is used in, programming languages to map the, variable and object., , • Understand what is Scoping, • Able to implement the LEGB rule, • Understand what is module, • Understand the implementation of, access control in programming language, , 3.1 Introduction, , Programming languages keeps track, of all these mappings with namespaces., Namespaces are containers for mapping, names of variables to objects. You can think, of them as dictionaries, containing list, of words and its meanings. The words are, mapped with its meaning in dictionaries, whereas names are mapped with objects, (name : = object) in programming language., This allows access to objects by names you, choose to assign to them., , Scope refers to the visibility of, variables, parameters and functions in one, part of a program to another part of the, same program. In other words, which parts, of your program can see or use it. Normally,, every variable defined in a program has, global scope. Once defined, every part of, your program can access that variable. But it, is a good practice to limit a variable's scope, to a single definition. This way, changes, inside the function can't affect the variable, on the outside of the function in unexpected, ways., , In the following example, a is first, mapped to the integer 5. In this case, a is the, variable name, while the integer value 5 is, the object., , 3.2 Variable Scope, , Then, b is set equal to a. This actually, means that b is now bound to the same, integer value as a, which is 5., , To understand the scope of variables, in a programming language, it is important, to learn about what variables really are., Essentially, they're addresses (references, or, pointers), to an object in memory. When, , 1. a:=5, 2. b:=a, 21, , Chapter 3.indd 21, , 20-02-2019 15:18:40
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the error “name ‘a’ is not defined”. This is, because the lifetime of the variable is only till, the end of the procedure. Also, the duration, for which a variable is alive is called its ‘life, time’., , Mapping, , a, , 5, , Now consider the following extension, of the above statements, , Scope also defines the order in which, variables have to be mapped to the object, in order to obtain the value. Let us take a, simple example as shown below:, , 1. a:=5, , 1. x:= 'outer x variable', , 2. b:=a, , 2. display():, , 3. a:=3, , 3., , x:= 'inner x variable', , If you then change a to be equal to 3,, a budding programmer might expect b also, be equal to 3, but that is not the case. b is still, mapped (or pointing) to the integer value of, 5. The only thing that changed is a, which is, now mapped to the integer value 3., , 4., , print x, , 5. display(), When the above statements are executed the, statement (4) and (5) display the result as, , Output, outer x variable, , Mapping after changing the value of a, , a, , 3, , b, , 5, , inner x variable, Above statements give different, outputs because the same variable name x, resides in different scopes, one inside the, function display() and the other in the upper, level. The value ‘outer xvariable’ is printed, when x is referenced outside the function, definition. Whereas when display() gets, executed, ‘inner x variable’ is printed which, is the x value inside the function definition., From the above example, we can guess that, there is a rule followed, in order to decide, from which scope a variable has to be picked., , The scope of a variable is that part of, the code where it is visible. Actually, to refer, to it, you don’t need to use any prefixes then., Let’s take an example,, , The LEGB rule is used to decide the, order in which the scopes are to be searched, for scope resolution. The scopes are listed, below in terms of hierarchy (highest to, lowest)., , 1. Disp():, 2., , a:=7, , When you try to display the value of, a outside the procedure the program flags, XII Std Computer Science, , Chapter 3.indd 22, , LEGB rule, , 3.3, , b, , 22, , 20-02-2019 15:18:40
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Local(L), , Defined inside function/class, , Enclosed(E), , Defined inside enclosing functions (Nested function concept), , Global(G), , Defined at the uppermost level, , Built-in (B), , Reserved names in built-in functions (modules), BUILT-IN, GLOBAL, ENCLOSED, LOCAL, , 3.4 Types of Variable Scope, There are 4 types of Variable Scope, let’s discuss them one by one:, , 3.4.1 Local Scope, Local scope refers to variables defined in current function. Always, a function will first, look up for a variable name in its local scope. Only if it does not find it there, the outer scopes, are checked., Look at this example, 1. Disp():, 2., , a:=7, , 3., , print a, , 4. Disp(), , Entire program, Disp( ):, a:=7, print a, , Output of the Program, 7, , Disp ( ), , On execution of the above code the variable a displays the value 7, because it is defined, and available in the local scope., , 23, , Chapter 3.indd 23, , Scoping, , 20-02-2019 15:18:40
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3.4.2 Global Scope, A variable which is declared outside of all the functions in a program is known as global, variable. This means, global variable can be accessed inside or outside of all the functions in a, program. Consider the following example, 1. a:=10, 2. Disp():, 3. a:=7, 4. print a, 5. Disp(), , Entire program, , Output of the Program, 7, , a:=10, Disp( ), a:=7, print a, , 10, , Disp 1( ):, print a, , 6. print a, On execution of the above code the variable a which is defined inside the function, displays the value 7 for the function call Disp() and then it displays 10, because a is defined in, global scope., , 3.4.3. Enclosed Scope, All programming languages permit functions to be nested. A function (method) with, in another function is called nested function. A variable which is declared inside a function, which contains another function definition with in it, the inner function can also access the, variable of the outer function. This scope is called enclosed scope., When a compiler or interpreter search for a variable in a program, it first search Local,, and then search Enclosing scopes. Consider the following example, 1. Disp():, 2. a:=10, 3. Disp1():, 4., , print a, , 5., , Disp1(), , 6. print a, , Entire program, Disp( ), a:=10, Disp 1( ):, print a, , Output of the Program, 10, 10, , Disp 1( ):, print a, Disp( ), , 7. Disp(), , XII Std Computer Science, , Chapter 3.indd 24, , 24, , 20-02-2019 15:18:40
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In the above example Disp1() is defined with in Disp(). The variable ‘a’ defined in Disp(), can be even used by Disp1() because it is also a member of Disp()., , 3.4.4. Built-in Scope, Finally, we discuss about the widest scope. The built-in scope has all the names that are, pre-loaded into the program scope when we start the compiler or interpreter. Any variable or, module which is defined in the library functions of a programming language has Built-in or, module scope. They are loaded as soon as the library files are imported to the program., Entire program, Built in/module scope, , Library files associated, with the software, , Disp( ), Disp 1( ):, print a, Disp 1( ):, print a, Disp( ), , Normally only Functions or modules come along with the software, as packages., Therefore they will come under Built in scope., , 3.5 Module, , independently. The examples of modules are, procedures, subroutines, and functions., , A module is a part of a program., Programs are composed of one or more, independently developed modules. A, single module can contain one or several, statements closely related each other., Modules work perfectly on individual level, and can be integrated with other modules., A software program can be divided into, modules to ease the job of programming, and debugging as well. A program can be, divided into small functional modules that, work together to get the output. The process, of subdividing a computer program into, separate sub-programs is called Modular, programming. Modular programming, enables programmers to divide up the, work and debug pieces of the program, , 3.5.1 Characteristics of Modules, The following are the desirable, characteristics of a module., 1. Modules contain instructions, processing, logic, and data., 2. Modules can be separately compiled and, stored in a library., 3. Modules can be included in a program., 4. Module segments can be used by, invoking a name and some parameters., 5. Module segments can be used by other, modules., , 25, , Chapter 3.indd 25, , Scoping, , 20-02-2019 15:18:40
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3.5.2 The benefits of using modular, programming include, , oriented languages, such as C++ and Java,, control the access to class members by, public, private and protected keywords., Private members of a class are denied access, from the outside the class. They can be, handled only from within the class., , • Less code to be written., • A single procedure can be developed for, reuse, eliminating the need to retype the, code many times., , Public members (generally methods, declared in a class) are accessible from, outside the class. The object of the same class, is required to invoke a public method. This, arrangement of private instance variables, and public methods ensures the principle of, data encapsulation., , • Programs can be designed more easily, because a small team deals with only a, small part of the entire code., • Modular programming allows many, programmers to collaborate on the same, application., • The code is stored across multiple files., , Protected members of a class are, accessible from within the class and are also, available to its sub-classes. No other process, is permitted access to it. This enables specific, resources of the parent class to be inherited, by the child class., , • Code is short, simple and easy to, understand., • Errors can easily be identified, as they, are localized to a subroutine or function., • The same code can be used in many, applications., , Python doesn't have any mechanism, that effectively restricts access to any instance, variable or method. Python prescribes a, convention of prefixing the name of the, variable or method with single or double, underscore to emulate the behaviour of, protected and private access specifiers., , • The scoping of variables can easily be, controlled., , 3.5.3 Access Control, Access control is a security technique, that regulates who or what can view or use, resources in a computing environment., It is a fundamental concept in security, that minimizes risk to the object. In other, words access control is a selective restriction, of access to data. IN Object oriented, programming languages it is implemented, through access modifiers. Classical object-, , XII Std Computer Science, , Chapter 3.indd 26, , All members in a Python class are, public by default, whereas by default in C++, and java they are private. Any member can be, accessed from outside the class environment, in Python which is not possible in C++ and, java., , 26, , 20-02-2019 15:18:40
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Points to remember:, • Scope refers to the visibility of variables, parameters and functions in one part of a, program to another part of the same program., • The process of binding a variable name with an object is called mapping.= (equal to, sign) is used in programming languages to map the variable and object., • Namespaces are containers for mapping names of variables to objects., • The scope of a variable is that part of the code where it is visible., • The LEGB rule is used to decide the order in which the scopes are to be searched for, scope resolution., • Local scope refers to variables defined in current function., • A variable which is declared outside of all the functions in a program is known as, global variable., • A function (method) with in another function is called nested function., • A variable which is declared inside a function which contains another function, definition with in it, the inner function can also access the variable of the outer, function. This scope is called enclosed scope., • Built-in scope has all the names that are pre-loaded into program scope when we start, the compiler or interpreter., • A module is a part of a program. Programs are composed of one or more independently, developed modules., • The process of subdividing a computer program into separate sub-programs is called, Modular programming., • Access control is a security technique that regulates who or what can view or use, resources in a computing environment. It is a fundamental concept in security that, minimizes risk to the object., • Public members (generally methods declared in a class) are accessible from outside, the class., • Protected members of a class are accessible from within the class and are also available, to its sub-classes, • Private members of a class are denied access from the outside the class. They can be, handled only from within the class., • Python prescribes a convention of prefixing the name of the variable/method with, single or double underscore to emulate the behaviour of protected and private access, specifiers., • C++ and Java, control the access to class members by public, private and protected, keywords, • All members in a Python class are public by default whereas by default in C++ and java, all members are private., , 27, , Chapter 3.indd 27, , Scoping, , 20-02-2019 15:18:41
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Hands on Practice, 1. Observe the following diagram and Write the pseudo code for the following, sum( ), num 1:=20, sum1( ), num 1:=nim 1 + 10, sum2( ), num 1: = num 1 + 10, , sum2( ), sum1( ), num1:=10, sum( ), print num 1, , Evaluation, Part - I, Choose the best answer, , (1 Mark), , 1. Which of the following refers to the visibility of variablesin one part of a program to, another part of the same program., (A) Scope, , (B) Memory, , (C) Address, , (D) Accessibility, , 2. The process of binding a variable name with an object is called, (A) Scope, , (B) Mapping, , (C) late binding, , (D) early binding, , 3. Which of the following is used in programming languages to map the variable and object?, (A) ::, , (B) :=, , (C) =, , (D) ==, , 4. Containers for mapping names of variables to objects is called, (A) Scope, , (B) Mapping, , (C) Binding, , (D) Namespaces, , 5. Which scope refers to variables defined in current function?, (A) Local Scope, , (B) Global scope, , (C) Module scope, , (D) Function Scope, , XII Std Computer Science, , Chapter 3.indd 28, , 28, , 20-02-2019 15:18:41
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6. The process of subdividing a computer program into separate sub-programs is called, (A) Procedural Programming, , (B) Modular programming, , (C)Event Driven Programming, , (D) Object oriented Programming, , 7. Which of the following security technique that regulates who canuse resources in a, computing environment?, (A) Password, , (B)Authentication, , (C) Access control, , (D) Certification, , 8. Which of the following members of a class can be handled only from within the class?, (A) Public members, , (B)Protected members, , (C) Secured members, , (D) Private members, , 9. Which members are accessible from outside the class?, (A) Public members, , (B)Protected members, , (C) Secured members, , (D) Private members, , 10. The members that are accessible from within the class and are also available to its subclasses is called, (A) Public members, , (B)Protected members, , (C) Secured members, , (D) Private members, Part - II, , Answer the following questions, , (2 Marks), , 1. What is a scope?, 2. Why scope should be used for variable. State the reason., 3. What is Mapping?, 4. What do you mean by Namespaces?, 5. How Python represents the private and protected Access specifiers?, Part - III, Answer the following questions, , (3 Marks), , 1. Define Local scope with an example., 2. Define Global scope with an example., 3. Define Enclosed scope with an example., 29, , Chapter 3.indd 29, , Scoping, , 20-02-2019 15:18:41
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4. Why access control is required?, 5. Identify the scope of the variables in the following pseudo code and write its, output, color:= Red, mycolor():, b:=Blue, myfavcolor():, g:=Green, printcolor, b, g, myfavcolor(), printcolor, b, mycolor(), print color, Part - IV, Answer the following questions, 1, , (5Marks), , Explain the types of scopes for variable or LEGB rule with example., , 2. Write any Five Characteristics of Modules., 3. Write any five benefits in using modular programming., REFERENCES, 1., , Data Structures and Algorithms in Python By Michael T.Goodrich, RobertoTamassia and, Michael H. Goldwasser., , 2., , Data Structure and Algorithmic Thinking in Python By Narasimha Karumanchi, , 3., , https://www.python.org, , XII Std Computer Science, , Chapter 3.indd 30, , 30, , 20-02-2019 15:18:41
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Unit, , I, , CHAPTER 4, ALGORITHMIC STRATEGIES, , Learning Objectives, , Search, , At the end of this chapter the students will, be able to:, • Know the basics and, perspective of algorithms., , Sort, , technical, , • Understand the efficiency, time and, space complexity of an algorithm., , Insert, , • Develop and analyze algorithms for, searching and sorting., , To search an item in a data, structure using linear and, binary search., To sort items in a certain, order using the methods such, as bubble sort, insertion sort,, selection sort, etc., To insert an item (s) in a data, structure., , Update To update an existing item (s), in a data structure., , • Learn about dynamic programming, through algorithmic approach., , Delete, , 4.1 Introduction to Algorithmic, strategies, , To delete an existing item (s) in, a data structure., , The way of defining an algorithm is, called algorithmic strategy. For example to, calculate factorial for the given value n then, it can be done by defining the function to, calculate factorial once for the iteration-1, then it can be called recursively until the, number of required iteration is reached., , An algorithm is a finite set of, instructions to accomplish a particular task., It is a step-by-step procedure for solving, a given problem. An algorithm can be, implemented in any suitable programming, language., , The word Algorithm comes, from the name of a Persian author,, Abu Jafar Mohammed ibn Musa al, Khowarizmi(c. 825 AD(CE)), who, wrote a textbook on mathematics. The, word Algorithm has come to refer to a, method to solve a problem., , Algorithms must have input,, output and should satisfy the following, characteristics such as definiteness,, correctness and effectiveness. Data are, maintained and manipulated effectively, through data structures. Algorithms can be, developed to store, manipulate and retrieve, data from such data structures. Examples, for data structures are arrays, structures, list,, tuples, dictionary etc., , 4.1.1Characteristics of an Algorithm, An algorithm should have the, following characteristics:, 31, , Chapter 4.indd 31, , 20-02-2019 15:19:14
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Input, , Zero or more quantities, to be supplied., , Output, , At least one quantity is, produced., , Finiteness, , Algorithms, must, terminate after, finite, number of steps., , Definiteness, , All operations should be, well defined. For example, operations involving, division by zero or, taking square root for, negative number are, unacceptable., , Effectiveness, , Every instruction must, be carried out effectively., , Correctness, , The algorithms should be, error free., , Simplicity, , Easy to implement., , Independent, , 4.1.2 Writing an Algorithm, Algorithms are generic and not, limited to computer alone. It can be used in, various real time activities also. Knowingly or, unknowingly we perform many algorithms, in our daily life such as packing books in, school bag, finding shortest path to search, a place, scheduling day-to-day activities,, preparation for examination, etc. As we, know that all programming languages share, basic code constructs like conditions and, iterations can be used to write an algorithm., A typical algorithm is shown in the following, Figure 4.1., , Unambiguous Algorithm should be, clear and unambiguous., Each of its steps and their, inputs/outputs should, be clear and must lead to, only one meaning., Feasibility, , Should be feasible with, the available resources., , Portable, , An algorithm should be, generic, independent of, any programming, language or an operating, system able to handle all, range of inputs., , XII Std Computer Science, , Chapter 4.indd 32, , An algorithm should, have, step-by-step, directions, which should, be independent of any, programming, code., , Input, Example, , Process, , Output, , A Typical Algorithm, , Consider the example of Coffee, preparation. To make coffee, we need to, have the following ingredients: Water, milk,, coffee powder and sugar. These ingredients, are the inputs of an algorithm. Preparing a, cup of coffee is called process. The output of, this process is coffee., The procedure for preparing coffee is as, follows:, 1., , Take a bowl with coffee powder, , 2., , Boil the water and pour it into the, bowl, , 32, , 20-02-2019 15:19:14
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3., , Filter it, , Algorithm, , Program, , 4., , Boil milk, , 5., , Mix sugar and filtered coffee along, with boiled milk, , 6., , Pour the coffee into the cup to serve, , • Algorithm, helps to solve a, given problem, logically and, it can be, contrasted with, the program, , • Program is an, expression of, algorithm in a, programming, language, , This kind of procedure can be, represented using an algorithm. Thus,, the algorithm consists of step-step-by, instructions that are required to accomplish, a task and helps the programmer to develop, the program., , • Algorithm can, • Algorithm, be categorized, can be, based on their, implemented, implementation, by structured, methods, design, or object, techniques etc, oriented, programming, approach, , Problem: Design an algorithm to find, square of the given number and display the, result., The algorithm can be written as:, Step 1 – start the process, Step 2 – get the input x, Step 3 –calculate the square by, multiplying the input value ie.,, square ← x* x, Step 4 − display the result square, Step 5 − stop, Algorithm could be designed to get, a solution of a given problem. A problem, can be solved in many ways. Among many, algorithms the optimistic one can be taken, for implementation., , • Program, should be, written for, the selected, language with, specific syntax, , • Algorithm, resembles a, pseudo code, which can be, implemented in, any language, , • Program, is more, specific to a, programming, language, , Table 4.1 Algorithm Vs Program, 4.1.3. Analysis of Algorithm, , An algorithm that yields, expected output for a valid input, is called an algorithmic solution., , Computer resources are limited., Efficiency of an algorithm is defined by the, utilization of time and space complexity., , 33, , Chapter 4.indd 33, , • There is no, specific rules, for algorithm, writing but, some guidelines, should be, followed., , Algorithmic Strategies, , 20-02-2019 15:19:14
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Analysis of an algorithm usually deals with, the running and execution time of various, operations involved. The running time of, an operation is calculated as how many, programming instructions executed per, operation., , gives the running time and/or the storage, space required by the algorithm in terms of, n as the size of input data., 4.2.1 Time Complexity, The Time complexity of an algorithm, is given by the number of steps taken by the, algorithm to complete the process., , Analysis, of, algorithms, and, performance evaluation can be divided into, two different phases:, , 4.2.2. Space Complexity, , 1. A Priori estimates: This is a theoretical, performance analysis of an algorithm., Efficiency of an algorithm is measured, by assuming the external factors., , Space complexity of an algorithm, is the amount of memory required to run, to its completion. The space required by, an algorithm is equal to the sum of the, following two components:, , 2. A Posteriori testing: This is called, performance measurement. In this, analysis, actual statistics like running, time and required for the algorithm, executions are collected., , A fixed part is defined as the total, space required to store certain data and, variables for an algorithm. For example,, simple variables and constants used in an, algorithm., , An estimation of the time and, space complexities of an algorithm, for varying input sizes is called, algorithm analysis., , A variable part is defined as the, total space required by variables, which sizes, depends on the problem and its iteration., For example: recursion used to calculate, factorial of a given value n., , 4.2 Complexity of an, Algorithm, , 4.3 Efficiency of an algorithm, , Suppose A is an algorithm and n is, the size of input data, the time and space, used by the algorithm A are the two main, factors, which decide the efficiency of A., , Computer resources are limited that, should be utilized efficiently. The efficiency, of an algorithm is defined as the number, of computational resources used by the, algorithm. An algorithm must be analyzed to, determine its resource usage. The efficiency, of an algorithm can be measured based on, the usage of different resources., , Time Factor -Time is measured by, counting the number of key, operations like comparisons, in the sorting algorithm., Space Factor - Space is measured by the, maximum memory space required by the, algorithm., , For maximum efficiency of algorithm, we wish to minimize resource usage. The, important resources such as time and space, complexity cannot be compared directly,, , The complexity of an algorithm f (n), XII Std Computer Science, , Chapter 4.indd 34, , 34, , 20-02-2019 15:19:14
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so time and space complexity could be, considered for an algorithmic efficiency., , tradeoff is a way of solving in less time by, using more storage space or by solving, a given algorithm in very little space by, spending more time., , 4.3.1 Method for determining Efficiency, , To solve a given programming, problem, many different algorithms may, be used. Some of these algorithms may, be extremely time-efficient and others, extremely space-efficient., , The efficiency of an algorithm depends, on how efficiently it uses time and memory, space., The time efficiency of an algorithm is, measured by different factors. For example,, write a program for a defined algorithm,, execute it by using any programming, language, and measure the total time it takes, to run. The execution time that you measure, in this case would depend on a number of, factors such as:, , Time/space trade off refers to a, situation where you can reduce the use, of memory at the cost of slower program, execution, or reduce the running time at the, cost of increased memory usage., The best algorithm to solve, a given problem is one that, requires less space in memory, and takes less time to execute its, instructions to generate output., , • Speed of the machine, • C, ompiler and other system Software, tools, • Operating System, , 4.3.3 Asymptotic Notations, , • Programming language used, , Asymptotic Notations are languages, that uses meaningful statements about time, and space complexity. The following three, asymptotic notations are mostly used to, represent time complexity of algorithms:, , • Volume of data required, However, to determine how, efficiently an algorithm solves a given, problem, you would like to determine how, the execution time is affected by the nature, of the algorithm. Therefore, we need to, develop fundamental laws that determine, the efficiency of a program in terms of the, nature of the underlying algorithm., , (i) Big O, Big O is often used to describe the, worst-case of an algorithm., (ii) Big Ω, Big Omega is the reverse Big O, if, Bi O is used to describe the upper bound, (worst - case) of a asymptotic function, Big, Omega is used to describe the lower bound, (best-case)., , A way of designing algorithm, is called algorithmic strategy, 4.3.2 Space-Time tradeoff, A, , space-time, , or, , time-memory, 35, , Chapter 4.indd 35, , Algorithmic Strategies, , 20-02-2019 15:19:14
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(iii) Big Θ, , If the element not found then maximum, number of comparison, =n, , When an algorithm has a complexity, with lower bound = upper bound, say that an, algorithm has a complexity O (n log n) and, Ω (n log n), it’s actually has the complexity, Θ (n log n), which means the running time, of that algorithm always falls in n log n in, the best-case and worst-case., , Therefore, average, comparisons, , number of, = (n + 1)/2, , Hence the average case efficiency will, be expressed as O (n)., , 4.4 Algorithm for Searching, Techniques, , 4.3.4 , Best, Worst, and Average ease, E f f i ci enc y, , 4.4.1 Linear Search, , Let us assume a list of n number of, values stored in an array. Suppose if we want, to search a particular element in this list,, the algorithm that search the key element, in the list among n elements, by comparing, the key element with each element in the list, sequentially., , Linear search also called sequential, search is a sequential method for finding a, particular value in a list. This method checks, the search element with each element in, sequence until the desired element is found, or the list is exhausted. In this searching, algorithm, list need not be ordered., , The best case would be if the first, element in the list matches with the key, element to be searched in a list of elements., The efficiency in that case would be expressed, as O(1) because only one comparison is, enough., , Pseudo code, 1. Traverse the array using for loop, 2. In every iteration, compare the target, search key value with the current value, of the list., • If the values match, display the current, index and value of the array, , Similarly, the worst case in this, scenario would be if the complete list is, searched and the element is found only, at the end of the list or is not found in the, list. The efficiency of an algorithm in that, case would be expressed as O(n) because, n comparisons required to complete the, search., , • If the values do not match, move on to, the next array element., 3. If no match is found, display the search, element not found., To search the number 25 in the array, given below, linear search will go step by, step in a sequential order starting from the, first element in the given array if the search, element is found that index is returned, otherwise the search is continued till the last, index of the array. In this example number, 25 is found at index number 3., , The average case efficiency of an, algorithm can be obtained by finding the, average number of comparisons as given, below:, Minimum number of comparisons = 1, Maximum number of comparisons = n, XII Std Computer Science, , Chapter 4.indd 36, , 36, , 20-02-2019 15:19:14
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index, , 0, , 1, , 2, , 3, , 4, , values, , 10, , 12, , 20, , 25, , 30, , Example 1:, Input: values[] = {5, 34, 65, 12, 77, 35}, target = 77, Output: 4, Example 2:, Input: values[] = {101, 392, 1, 54, 32, 22, 90, 93}, target = 200, Output: -1 (not found), 4.4.2. Binary Search, , 3., , Binary search also called half-interval, search algorithm. It finds the position of a, search element within a sorted array. The, binary search algorithm can be done as, divide-and-conquer search algorithm and, executes in logarithmic time., , Binary Search Working principles, List of elements in an array must be, sorted first for Binary search. The following, example describes the step by step operation, of binary search. Consider the following, array of elemnts, the array is being sorted so, it enables to do the binary search algorithm., Let us assume that the search element is 60, and we need to search the location or index, of search element 60 using binary search., , Pseudo code for Binary search, 1., , Start with the middle element:, , • If the search element is equal to the, middle element of the array i.e., the, middle value = number of elements in, array/2, then return the index of the, middle element., , 10 20 30 40 50 60 70 80 90 99, 0, , • If not, then compare the middle element, with the search value,, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , mid = low + (high - low) / 2, Here it is, 0 + (9 - 0 ) / 2 = 4 (fractional, part ignored). So, 4 is the mid value of the, array., , • If the search element is less than the, number in the middle index, then select, the elements to the left side of the middle, index, and start with Step-1., , 10 20 30 40 50 60 70 80 90 99, , When a match is found, display success, message with the index of the element, matched., , 0, , 37, , Chapter 4.indd 37, , 1, , First, we find index of middle element of the, array by using this formula :, , • If the search element is greater than the, number in the middle index, then select, the elements to the right side of the, middle index, and go to Step-1., , 2., , If no match is found for all comparisons,, then display unsuccessful message., , 1, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , Algorithmic Strategies, , 20-02-2019 15:19:15
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Now compare the search element, with the value stored at mid value location, 4. The value stored at location or index 4 is, 50, which is not match with search element., As the search value 60 is greater than 50., , 10 20 30 40 50 60 70 80 90 99, 0, , 1, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , Now we change our low to mid + 1 and find, the new mid value again using the formula., , 10 20 30 40 50 60 70 80 90 99, 3, , 4, , 5, , 6, , 7, , 8, , 9, , The value stored at location or index, 7 is not a match with search element, rather, it is more than what we are looking for. So,, the search element must be in the lower part, from the current mid value location, 10 20 30 40 50 60 70 80 90 99, 0, , 1, , 2, , 3, , 4, , 5, , 6, , 7, , 8, , 9, , Now the mid value is 5., , 9, , 2. If the current element is greater than the, next element of the array, swap them., , 10 20 30 40 50 60 70 80 90 99, 3, , 4, , 5, , 6, , 7, , 8, , 9, , 3. If the current element is less than the, next or right side of the element, move, to the next element. Go to Step 1 and, repeat until end of the index is reached., , Now we compare the value stored, at location 5 with our search element. We, found that it is a match., XII Std Computer Science, , Chapter 4.indd 38, , 8, , 1. Start with the first element i.e., index =, 0, compare the current element with the, next element of the array., , mid = low + (high - low)/2, , 2, , 7, , Pseudo code, , high = mid -1, , 1, , 6, , Assume list is an array of n elements., The swap function swaps the values of the, given array elements., , The search element still not found. Hence,, we calculated the mid again by using the, formula., , 0, , 5, , Bubble sort is a simple sorting, algorithm. The algorithm starts at the, beginning of the list of values stored in an, array. It compares each pair of adjacent, elements and swaps them if they are in the, unsorted order. This comparison and passed, to be continued until no swaps are needed,, which indicates that the list of values stored, in an array is sorted. The algorithm is a, comparison sort, is named for the way, smaller elements "bubble" to the top of the, list. Although the algorithm is simple, it is, too slow and less efficient when compared, to insertion sort and other sorting methods., , Our new mid is 7 now. We compare the value, stored at location 7 with our target value 31., , 2, , 4, , 4.5.1 Bubble sort algorithm, , mid = low + (high - low) / 2, , 1, , 3, , 4.5 Sorting Techniques, , low to mid + 1, , 0, , 2, , We can conclude that the search, element 60 is found at lcoation or index 5., For example if we take the search element, as 95, For this value this binary search, algorithm return unsuccessful result., , 10 20 30 40 50 60 70 80 90 99, 0, , 1, , 38, , 20-02-2019 15:19:15
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Let's consider an array with values {15, 11, 16, 12, 14, 13} Below, we have a pictorial, representation of how bubble sort will sort the given array., 15>11, So interchange, , 15 11 16 12 14 13, , 15>16, No swapping, , 15 11 16 12 14 13, , 16>12, So interchange, , 11 15 16 12, , 14 13, , 16>14, So interchange, , 11 15, , 16>13, So interchange, , 11 15 12 14 16, , 12 16 14 13, , 13, , 11 15 12 14 13 16, , The above pictorial example is for iteration-1. Similarly, remaining iteration can be, done. The final iteration will give the sorted array., At the end of all the iterations we will get the sorted values in an array as given below:, 11 12 13 14 15 16, , 4.5.2 Selection sort, The selection sort is a simple sorting algorithm that improves on the performance of, bubble sort by making only one exchange for every pass through the list. This algorithm will, first find the smallest elements in array and swap it with the element in the first position of an, array, then it will find the second smallest element and swap that element with the element in, the second position, and it will continue until the entire array is sorted in respective order., This algorithm repeatedly selects the next-smallest element and swaps in into the right, place for every pass. Hence it is called selection sort., Pseudo code, 1. Start from the first element i.e., index-0, we search the smallest element in the array, and, replace it with the element in the first position., 39, , Chapter 4.indd 39, , Algorithmic Strategies, , 20-02-2019 15:19:15
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2. Now we move on to the second element, position, and look for smallest element, present in the sub-array, from starting, index to till the last index of sub - array., , 4. This is repeated, until the array is, completely sorted., Let's consider an array with values {13, 16,, 11, 18, 14, 15}, , 3. Now replace the second smallest, identified in step-2 at the second position, in the or original array, or also called first, position in the sub array., Initial, array, 13, , At the, end First, pass, , Below, we have a pictorial representation of, how selection sort will sort the given array., , At the end, Second, pass, , At the end, Fourth, pass, , At the, end Fifth, pass, , 11, , 11, , 11, , 11, , 11, , 16, , 16, , 13, , 13, , 13, , 13, , 11, , 13, , 16, , 14, , 14, , 14, , 18, , 18, , 18, , 18, , 15, , 15, , 14, , 14, , 14, , 16, , 16, , 16, , 15, , 15, , 15, , 15, , 18, , 18, , In the first pass, the smallest element will be, 11, so it will be placed at the first position., , Finally we will get the sorted array, end of the pass as shown above diagram., , After that, next smallest element will, be searched from an array. Now we will get, 13 as the smallest, so it will be then placed at, the second position., , 4.5.3 Insertion sort, Insertion sort is a simple sorting, algorithm. It works by taking elements from, the list one by one and inserting then in, their correct position in to a new sorted list., This algorithm builds the final sorted array, at the end. This algorithm uses n-1 number, of passes to get the final sorted list as per the, pervious algorithm as we have discussed., , Then leaving the first element, next, smallest element will be searched, from, the remaining elements. We will get 13 as, the smallest, so it will be then placed at the, second position., , Pseudo for Insertion sort, , Then leaving 11 and 13 because they, are at the correct position, we will search for, the next smallest element from the rest of, the elements and put it at third position and, keep doing this until array is sorted., XII Std Computer Science, , Chapter 4.indd 40, , At the, end Third, pass, , Step 1 − If it is the first element, it is already, sorted., Step 2 − Pick next element, 40, , 20-02-2019 15:19:15
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Step 3 − Compare with all elements in the, sorted sub-list, , Step 5 − Insert the value, Step 6 − Repeat until list is sorted, , Step 4 − Shift all the elements in the sorted, sub-list that is greater than the value to be, sorted, 44, , 16, , 83, , 07, , 67, , 21, , 34, , 45, , 10, , 16, , 44, , 83, , 07, , 67, , 21, , 34, , 45, , 10, , Assume 44 is a soted, list of 1 item, inserted 16, , 16, , 44, , 83, , 07, , 67, , 21, , 34, , 45, , 10, , inserted 83, , 07, , 16, , 44, , 83, , 67, , 21, , 34, , 45, , 10, , inserted 07, , 07, , 16, , 44, , 67, , 83, , 21, , 34, , 45, , 10, , inserted 67, , 07, , 16, , 21, , 44, , 67, , 83, , 34, , 45, , 10, , inserted 21, , 07, , 16, , 21, , 34, , 44, , 67, , 83, , 45, , 10, , inserted 34, , 07, , 16, , 21, , 34, , 44, , 45, , 67, , 83, , 10, , inserted 45, , 07, , 10, , 16, , 21, , 34, , 44, , 45, , 67, , 83, , inserted 10, , At the end of the pass the insertion, sort algorithm gives the sorted output in, ascending order as shown below:, 07, , 10, , 4.6., , 16, , 21, , 34, , 44, , 45, , 67, , algorithm will try to check the results of, the previously solved sub-problems. The, solutions of overlapped sub-problems are, combined in order to get the better solution., , 83, , Steps to do Dynamic programming, , Dynamic programming, , • The given problem will be divided into, smaller overlapping sub-problems., , Dynamic programming is an, algorithmic design method that can be, used when the solution to a problem can, be viewed as the result of a sequence of, decisions. Dynamic programming approach, is similar to divide and conquer. The given, problem is divided into smaller and yet, smaller possible sub-problems., , • An optimum solution for the given, problem can be achieved by using result, of smaller sub-problem., • Dynamic algorithms uses Memoization., Note, Memoization or memoisation, is an optimization technique used, primarily to speed up computer, programs by storing the results of, expensive function calls and returning, the cached result when the same inputs, occur again., , Dynamic programming is used, whenever problems can be divided into, similar sub-problems. so that their results, can be re-used to complete the process., Dynamic programming approaches are, used to find the solution in optimized way., For every inner sub problem, dynamic, 41, , Chapter 4.indd 41, , Algorithmic Strategies, , 20-02-2019 15:19:15
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4.6.1 Fibonacci Series – An example, , Initialize f0=0, f1 =1, , Fibonacci series generates the, subsequent number by adding two previous, numbers. Fibonacci series starts from two, numbers − Fib 0 & Fib 1. The initial values, of Fib 0 & Fib 1 can be taken as 0 and 1., , step-1: Print the initial values of Fibonacci, f0 and f1, step-2: Calculate fibanocci fib ← f0 + f1, step-3: Assign f0← f1, f1← fib, , Fibonacci series satisfies the following, conditions :, , step-4: Print the next consecutive value of, fibanocci fib, , Fibn = Fibn-1 + Fibn-2, , step-5: Goto step-2 and repeat until the, specified number of terms generated, , Hence, a Fibonacci series for the n value 8, can look like this, , For example if we generate fibobnacci series, upto 10 digits, the algorithm will generate, the series as shown below:, , Fib8 = 0 1 1 2 3 5 8 13, 4.6.2 Fibonacci Iterative Algorithm with, Dynamic programming approach, , The Fibonacci series is : 0 1 1 2 3 5 8 13 21, 34 55, , The following example shows a, simple Dynamic programming approach, for the generation of Fibonacci series., , Points to remember:, • Abstract Data type (ADT) is a type (or class) for objects whose behavior is defined by, a set of value and a set of operations., • The definition of ADT only mentions what operations are to be performed but not, how these operations will be implemented., • ADT does not specify how data will be organized in memory and what algorithms, will be used for implementing the operations, • Constructors are functions that build the abstract data type., • Selectors are functions that retrieve information from the data type., • Concrete data types or structures (CDT's) are direct implementations of a relatively, simple concept., • Abstract Data Types (ADT's) offer a high level view (and use) of a concept independent, of its implementation., • A concrete data type is a data type whose representation is known and in abstract data, type the representation of a data type is unknown, • Pair is a compound structure which is made up of list or Tuple, , XII Std Computer Science, , Chapter 4.indd 42, , 42, , 20-02-2019 15:19:15
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Points to remember:, • List in is constructed by placing expressions within square brackets separated by, commas, • The elements of a list can be accessed in two ways. The first way is via multiple, assignment and the second method is by the element selection operator, • Bundling two values together into one can be considered as a pair, • List does not allow to name the various parts of a multi-item object., , Evaluation, Part - I, Choose the best answer:, , (1 Marks), , 1. The word comes from the name of a Persian mathematician Abu Ja’far Mohammed ibn-i, Musa al Khowarizmi is called?, (A) Flowchart, , (B) Flow, , (C) Algorithm, , (D) Syntax, , 2. From the following sorting algorithms which algorithm needs the minimum number of, swaps?, (A) Bubble sort, , (B) Quick sort, , (C) Merge sort, , (D) Selection sort, , 3. Two main measures for the efficiency of an algorithm are, (A) Processor and memory, , (B) Complexity and capacity, , (C) Time and space, , (D) Data and space, , 4. The complexity of linear search algorithm is, (A) O(n), , (B) O(log n), , (C) O(n2), , (D) O(n log n), , 5. From the following sorting algorithms which has the lowest worst case complexity?, (A) Bubble sort, , (B) Quick sort, , (C) Merge sort, , (D) Selection sort, , 6. Which of the following is not a stable sorting algorithm?, (A) Insertion sort, , (B) Selection sort, , (C) Bubble sort, , (D) Merge sort, , (C) θ (n2), , (D) θ (n(logn) 2), , 7. Time complexity of bubble sort in best case is, (A) θ (n), , (B) θ (nlogn), , 43, , Chapter 4.indd 43, , Algorithmic Strategies, , 20-02-2019 15:19:16
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8. The Θ notation in asymptotic evaluation represents, (A) Base case, , (B) Average case, , (C) Worst case, , (D) NULL case, , 9. If a problem can be broken into subproblems which are reused several times, the problem, possesses which property?, (A) Overlapping subproblems, , (B) Optimal substructure, , (C) Memoization, , (D) Greedy, , 10. In dynamic programming, the technique of storing the previously calculated values is, called ?, (A) Saving value property, , (B) Storing value property, , (C) Memoization, , (D) Mapping, Part - II, , Answer the following questions, , (2 Marks), , 1. What is an Algorithm?, 2. Define Pseudo code., 3. Who is an Algorist?, 4. What is Sorting?, 5. What is searching? Write its types., Part - III, Answer the following questions, , (3 Marks), , 1. List the characteristics of an algorithm., 2. Discuss about Algorithmic complexity and its types., 3. What are the factors that influence time and space complexity., 4. Write a note on Asymptotic notation., 5. What do you understand by Dynamic programming?, , XII Std Computer Science, , Chapter 4.indd 44, , 44, , 20-02-2019 15:19:16
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Part - IV, Answer the following questions, , (5Marks), , 1. Explain the characteristics of an algorithm., 2. Discuss about Linear search algorithm., 3. What is Binary search? Discuss with example., 4. Explain the Bubble sort algorithm with example., 5. Explain the concept of Dynamic programming with suitable example., , Reference Books, 1. Fundamentals Computer Algorithms, Ellis Horowitz, Sartaj Sahni, Sanguthevar,, Rajasekaran, Second Edition, University press (India) Limited, 2013., 2. Design and Analysis of Algorithms, S. Sridhar, Oxford University Press, 2015, , Web References, www.wickipedia.org, , CASE STUDY/ STUDENT’S ACTIVITY, 1. Create an algorithm for grading systems of your class student’s Quarterly examination, marks by satisfying all necessary conditions., , 45, , Chapter 4.indd 45, , Algorithmic Strategies, , 20-02-2019 15:19:16
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Why Python in standard XII curriculum?, This is the question that is fretting, the minds of teachers and students., The present book is organized in, such a way that even a novice reader can, grasp and work on python programming., , Testimonies, • "Python has been an important part, of Google since the beginning and, remains so as the system grows and, evolves. Today dozens of Google, engineers use Python, and we're, looking for more people with skills, in this language." -- Peter Norvig,, director of search quality at Google,, Inc., • "Python is fast enough for our, site and allows us to produce, maintainable features in record times,, with a minimum of developers,", -- Cuong Do, Software Architect,, YouTube.com, Python’s, popularity has seen, a steady and unflagging growth over, the recent years. Today, familiarity, with Python is an advantage for every, programmer, as Python has infiltrated, every niche and has useful roles to play in, any software solution., Python has experienced an, impressive growth as compared to the, other languages. The IEEE Spectrum, magazine published by the Institute, of Electrical & Electronics Engineers,, New York, ranks Python as the top language, for 2018, for the second consecutive year., , python interleaf page.indd 46, , The above statistical data has, maintained its grip with Python scoring, 100 and C++ language stands second, nipping at its heels with a 99.7 score., Python being popular is used by a number, of tech giants like Google, Instagram,, Pinterest, Yahoo, Disney, IBM, Nokia etc., 1. Python, , 100.0, , 2. C++, , 99.7, , 3. Java, , 97.5, , 4. C, , 96.7, , 5. C#, , 89.4, , 6. PHP, 7. R, , 84.9, 82.8, , 8. JavaScript, , 82.6, , 9. Go, , 76.4, , 10. Assembly, , 74.1, , Many businesses are advised to choose, Python for the following reasons:• Easy syntax and readability, • High level scripting language with, oops, • famous for enormous functions, addon modules, libraries, frameworks and, tool-kits., • Built-in functions supports scientific, computing., With the advent of computers,, there have been significant changes in the, way we work in almost all the fields. The, computerization has helped to improve, productivity and accelerate decision, making in every organization. Even for, individuals, be it engineers, doctors,, chartered accountants or homemakers, the, style of working has changed drastically., So as we go, let us accept the change and, move towards a brighter day ahead., , 20-02-2019 15:53:35
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Unit, , II, , CHAPTER 5, PYTHON VARIABLES AND OPERATORS, , Learning Objectives, After studying this lesson, students will be able to:, • Appreciate the use of Graphical User Interface (GUI) and Integrated Development, Environment (IDE) for creating Python programs., • Work in Interactive & Script mode for programming., • Create and assign values to variables., • Understand the concept and usage of different data types in Python., • Appreciate the importance and usage of different types of operators (Arithmetic, Relational, and Logical), • Creating Python expression (s) and statement (s)., , 5.1 Introduction, Python is a general purpose, programming language created by Guido, Van Rossum from CWI (Centrum Wiskunde, & Informatica) which is a National Research, Institute for Mathematics and Computer, Science in Netherlands. The language was, released in I991. Python got its name from a, BBC comedy series from seventies- “Monty, Python’s Flying Circus”. Python supports both, Procedural and Object Oriented programming, approaches., , 5.2 Key features of Python, It is a general purpose programming language which can be used for both scientific, and non-scientific programming., It is a platform independent programming language., The programs written in Python are easily readable and understandable., 47, , Chapter 5.indd 47, , 20-02-2019 15:19:39
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The version 3.x of Python IDLE (Integrated Development Learning Environment), is used to develop and run Python code. It can be downloaded from the web resource, www.python.org., , 5.3 Programming in Python, In Python, programs can be written in two ways namely Interactive mode and Script, mode. The Interactive mode allows us to write codes in Python command prompt (>>>), whereas in script mode programs can be written and stored as separate file with the extension, .py and executed. Script mode is used to create and edit python source file., , 5.3.1 Interactive mode Programming, In interactive mode Python code can be directly typed and the interpreter displays the, result(s) immediately. The interactive mode can also be used as a simple calculator., , (i) Invoking Python IDLE, The following command can be used to invoke Python IDLE from Window OS., Start → All Programs → Python 3.x → IDLE (Python 3.x), (Or), Click python, , Icon on the Desktop if available., , Now Python IDLE window appears as shown in the Figure 5.1, Menu Bar, , Tilte Bar, , Python prompt (>>>), , Python IDLE Window, The prompt (>>>) indicates that Interpreter is ready to accept instructions. Therefore,, the prompt on screen means IDLE is working in interactive mode. Now let us try as a simple, calculator by using a simple mathematical expressions., , XII Std Computer Science, , Chapter 5.indd 48, , 48, , 20-02-2019 15:19:40
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Example 1:, , Example 2:, , >>>print (“Python Programming Language”), Python Programming Language, >>>x=10, >>>y=20, >>>z=x + y, >>>print (“The Sum”, z), The Sum = 30, , >>> 5 + 10, 15, >>> 5 + 50 *10, 505, >>> 5 ** 2, 25, , Python Interactive Window, , 5.3.2 Script mode Programming, Basically, a script is a text file containing the Python statements. Python Scripts are, reusable code. Once the script is created, it can be executed again and again without retyping., The Scripts are editable., , (i) Creating Scripts in Python, 1., , Choose File → New File or press Ctrl + N in Python shell window., , 49, , Chapter 5.indd 49, , Python – Variables and Operators, , 20-02-2019 15:19:40
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Figure 5.3 – To create new File, 2., , An untitled blank script text editor will be displayed on screen as shown in Figure 5.3(a), , Figure 5.3(a) Untitled, blank Python script editor, 3., , Type the following code in Script editor, a =100, b = 350, c = a+b, print ("The Sum=", c), , , , XII Std Computer Science, , Chapter 5.indd 50, , a = 100, b = 350, c = a+b, print ("The Sum=", c), , Figure 5.4 – Python Sample code, , 50, , 20-02-2019 15:19:40
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(ii) Saving Python Script, (1), , Choose File → Save or Press Ctrl + S, , Figure 5.5 – To Save the file First time, (2), , Now, Save As dialog box appears on the screen as shown in the Figure 5.6, File Location, , File Name (demo1), File Type (Python file (.py)), Figure 5.6 – Save As Dialog Box, 51, , Chapter 5.indd 51, , Python – Variables and Operators, , 20-02-2019 15:19:40
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(3), , In the Save As dialog box, select the location where you want to save your Python code,, and type the file name in File Name box. Python files are by default saved with extension, .py. Thus, while creating Python scripts using Python Script editor, no need to specify, the file extension., , (4), , Finally, click Save button to save your Python script., , (iii) Executing Python Script, (1), , Choose Run → Run Module or Press F5, , a=100, b=350, c=a+b, print ("The Sum=", c), Figure 5.7 – To Execute Python Script, (2), , If your code has any error, it will be shown in red color in the IDLE window, and Python, describes the type of error occurred. To correct the errors, go back to Script editor, make, corrections, save the file using Ctrl + S or File → Save and execute it again., , (3), , For all error free code, the output will appear in the IDLE window of Python as shown in, Figure 5.8, , Output, , Figure 5.8 –Python Script Output Window, , XII Std Computer Science, , Chapter 5.indd 52, , 52, , 20-02-2019 15:19:40
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5.4 Input and Output Functions, A program needs to interact with the user to accomplish the desired task; this can be, achieved using Input-Output functions. The input() function helps to enter data at run time, by the user and the output function print() is used to display the result of the program on the, screen after execution., , 5.4.1 The print() function, In Python, the print() function is used to display result on the screen. The syntax for, print() is as follows:, , Example, print (“string to be displayed as output ” ), print (variable ), print (“String to be displayed as output ”, variable), print (“String1 ”, variable, “String 2”, variable, “String 3” ……), , Example, >>> print (“Welcome to Python Programming”), Welcome to Python Programming, >>> x = 5, >>> y = 6, >>> z = x + y, >>> print (z), 11, >>> print (“The sum = ”, z), The sum = 11, >>> print (“The sum of ”, x, “ and ”, y, “ is ”, z), The sum of 5 and 6 is 11, The print ( ) evaluates the expression before printing it on the monitor. The print, () displays an entire statement which is specified within print ( ). Comma ( , ) is used as a, separator in print ( ) to print more than one item., , 5.4.2 input() function, In Python, input( ) function is used to accept data as input at run time. The syntax for, input() function is,, Variable = input (“prompt string”), , 53, , Chapter 5.indd 53, , Python – Variables and Operators, , 20-02-2019 15:19:40
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Where, prompt string in the syntax is a statement or message to the user, to know what, input can be given., If a prompt string is used, it is displayed on the monitor; the user can provide expected, data from the input device. The input( ) takes whatever is typed from the keyboard and stores, the entered data in the given variable. If prompt string is not given in input( ) no message is, displayed on the screen, thus, the user will not know what is to be typed as input., Example 1:input( ) with prompt string, >>> city=input (“Enter Your City: ”), Enter Your City: Madurai, >>> print (“I am from “, city), I am from Madurai, Example 2:input( ) without prompt string, >>> city=input(), Rajarajan, >>> print (I am from", city), I am from Rajarajan, Note that in example-2, the input( ) is not having any prompt string, thus the user will, not know what is to be typed as input. If the user inputs irrelevant data as given in the above, example, then the output will be unexpected. So, to make your program more interactive,, provide prompt string with input( )., The input ( ) accepts all data as string or characters but not as numbers. If a numerical, value is entered, the input values should be explicitly converted into numeric data type. The, int( ) function is used to convert string data as integer data explicitly. We will learn about more, such functions in later chapters., , Example 3:, x = int (input(“Enter Number 1: ”)), y = int (input(“Enter Number 2: ”)), print (“The sum = ”, x+y), Output:, Enter Number 1: 34, Enter Number 2: 56, The sum = 90, XII Std Computer Science, , Chapter 5.indd 54, , 54, , 20-02-2019 15:19:40
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Example 4: Alternate method for the above program, x,y=int (input("Enter Number 1 :")),int(input("Enter Number 2:")), print ("X = ",x," Y = ",y), Output:, Enter Number 1 :30, Enter Number 2:50, X = 30 Y = 50, , 5.5 Comments in Python, In Python, comments begin with hash symbol (#). The lines that begins with # are, considered as comments and ignored by the Python interpreter. Comments may be single line, or no multi-lines. The multiline comments should be enclosed within a set of # as given below., # It is Single line Comment, # It is multiline comment, which contains more than one line #, , 5.6 Indentation, Python uses whitespace such as spaces and tabs to define program blocks whereas, other languages like C, C++, java use curly braces { } to indicate blocks of codes for class,, functions or body of the loops and block of selection command. The number of whitespaces, (spaces and tabs) in the indentation is not fixed, but all statements within the block must be, indented with same amount spaces., , 5.7 Tokens, Python breaks each logical line into a sequence of elementary lexical components, known as Tokens. The normal token types are, 1) Identifiers,, 2) Keywords,, 3) Operators,, 4) Delimiters and, 5) Literals., Whitespace separation is necessary between tokens, identifiers or keywords., , 5.7.1. Identifiers, An Identifier is a name used to identify a variable, function, class, module or object., , 55, , Chapter 5.indd 55, , Python – Variables and Operators, , 20-02-2019 15:19:40
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• An identifier must start with an alphabet (A..Z or a..z) or underscore ( _ )., • Identifiers may contain digits (0 .. 9), • Python identifiers are case sensitive i.e. uppercase and lowercase letters are distinct., • Identifiers must not be a python keyword., • Python does not allow punctuation character such as %,$, @ etc., within identifiers., , Example of valid identifiers, Sum, total_marks, regno, num1, , Example of invalid identifiers, 12Name, name$, total-mark, continue, , 5.7.2. Keywords, Keywords are special words used by Python interpreter to recognize the structure of, program. As these words have specific meaning for interpreter, they cannot be used for any, other purpose., Table 5.1 Python’s Keywords, false, , class, , finally, , is, , return, , none, , continue, , for, , lambda, , try, , true, , def, , from, , nonlocal, , while, , and, , del, , global, , not, , with, , as, , elif, , If, , or, , yield, , assert, , else, , import, , pass, , break, , except, , In, , raise, , 5.7.3 Operators, In computer programming languages operators are special symbols which represent, computations, conditional matching etc. The value of an operator used is called operands., Operators are categorized as Arithmetic, Relational, Logical, Assignment etc. Value and, variables when used with operator are known as operands., , (i) Arithmetic operators, An arithmetic operator is a mathematical operator that takes two operands and performs, a calculation on them. They are used for simple arithmetic. Most computer languages contain a, set of such operators that can be used within equations to perform different types of sequential, calculations., XII Std Computer Science, , Chapter 5.indd 56, , 56, , 20-02-2019 15:19:40
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Python supports the following Arithmetic operators., Operator - Operation, , Examples, , Result, , Assume a=100 and b=10. Evaluate the following expressions, + (Addition), , >>> a + b, , 110, , - (Subtraction), , >>>a – b, , 90, , * (Multiplication), , >>> a*b, , 1000, , / (Divisioin), , >>> a / b, , 10.0, , % (Modulus), , >>> a % 30, , 10, , ** (Exponent), , >>> a ** 2, , 10000, , // (Floor Division), , >>> a//30 (Integer Division), , 3, , Program 5.1 To test Arithmetic Operators:, #Demo Program to test Arithmetic Operators, a=100, b=10, print ("The Sum, = ",a+b), print ("The Difference = ",a-b), print ("The Product = ",a*b), print ("The Quotient = ",a/b), print ("The Remainder = ",a%30), print ("The Exponent = ",a**2), print ("The Floor Division =",a//30), #Program End, Output:, The Sum , = 110, The Difference, = 90, The Product , = 1000, The Quotient , = 10.0, The Remainder, = 10, The Exponent, = 10000, The Floor Division = 3, , (ii) Relational or Comparative operators, A Relational operator is also called as Comparative operator which checks the, relationship between two operands. If the relation is true, it returns True; otherwise it returns, False., 57, , Chapter 5.indd 57, , Python – Variables and Operators, , 20-02-2019 15:19:40
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Python supports following relational operators, Operator - Operation, , Examples, , Result, , Assume the value of a=100 and b=35. Evaluate the following expressions., == (is Equal), , >>> a==b, , False, , > (Greater than), , >>> a > b, , True, , < (Less than), , >>> a < b, , False, , >= (Greater than or Equal to), , >>> a >= b, , True, , <= (Less than or Equal to), , >>> a <= b, , False, , != (Not equal to), , >>> a != b, , True, , Coding 5.2 To test Relational Operators:, #Demo Program to test Relational Operators, a=int (input("Enter a Value for A:")), b=int (input("Enter a Value for B:")), print ("A = ",a," and B = ",b), print ("The a==b = ",a==b), print ("The a > b = ",a>b), print ("The a < b = ",a<b), print ("The a >= b = ",a>=b), print ("The a <= b = ",a<=0), print ("The a != b = ",a!=b), #Program End, Output:, Enter a Value for A:35, Enter a Value for B:56, A = 35 and B, = 56, The a==b , = False, The a > b , = False, The a < b , = True, The a >= b , = False, The a <= b , = False, The a != b , = True, , (iii) Logical operators, In python, Logical operators are used to perform logical operations on the given, relational expressions. There are three logical operators they are and, or and not., XII Std Computer Science, , Chapter 5.indd 58, , 58, , 20-02-2019 15:19:40
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Operator, , Example, , Result, , Assume a = 97 and b = 35, Evaluate the following Logical expressions, or, , >>> a>b or a==b, , True, , and, , >>> a>b and a==b, , False, , not, , >>> not a>b, , False i.e. Not True, , Program 5.3 To test Logical Operators:, Example – Code, , Example - Result, , #Demo Program to test Logical Operators, a=int (input("Enter a Value for A:")), b=int (input("Enter a Value for B:")), print ("A = ",a, " and b = ",b), print ("The a > b or a == b = ",a>b or a==b), print ("The a > b and a == b = ",a>b and a==b), print ("The not a > b, = ",not a>b), #Program End, , Enter a Value for A:50, Enter a Value for B:40, A = 50 and b = 40, The a > b or a == b = True, The a > b and a == b = False, The not a > b, = False, , (iv) Assignment operators, In Python, = is a simple assignment operator to assign values to variable. Let a = 5 and, b = 10 assigns the value 5 to a and 10 to b these two assignment statement can also be given, as a,b=5,10 that assigns the value 5 and 10 on the right to the variables a and b respectively., There are various compound operators in Python like +=, -=, *=, /=, %=, **= and //= are also, available., Operator, , Description, , Example, , =, , Assigns right side operands to left variable, , >>> x=10, >>> b=”Computer”, , +=, , Added and assign back the result, to left operand i.e. x=30, , >>> x+=20 # x=x+20, , -=, , Subtracted and assign back the, result to left operand i.e. x=25, , >>> x-=5 # x=x-5, , *=, , Multiplied and assign back the, result to left operand i.e. x=125, , >>> x*=5 # x=x*5, , /=, , Divided and assign back the, result to left operand i.e. x=62.5, , >>> x/=2 # x=x/2, , Assume x=10, , 59, , Chapter 5.indd 59, , Python – Variables and Operators, , 20-02-2019 15:19:40
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%=, , Taken modulus(Remainder) using, operands and assign the result, to left operand i.e. x=2.5, , two, , **=, , Performed exponential (power) calculation on, operators and assign value to the left operand >>> x**=2 # x=x**2, i.e. x=6.25, , //=, , Performed floor division on operators and, >>> x//=3, assign value to the left operand i.e. x=2.0, , >>> x%=3 # x=x%3, , Program 5.4 To test Assignment Operators:, Program Coding, , Output, , #Demo Program to test Assignment Operators, , Type a Value for X : 10, , x=int (input("Type a Value for X : ")), , X = 10, , print ("X = ",x), , The x is, , print ("The x is, , = 10, , The x += 20 is = 30, , =",x), , x+=20, , The x -= 5 is = 25, , print ("The x += 20 is =",x), , The x *= 5 is = 125, , x-=5, , The x /= 2 is = 62.5, , print ("The x -= 5 is = ",x), , The x %= 3 is = 2.5, , x*=5, , The x **= 2 is = 6.25, , print ("The x *= 5 is = ",x), , The x //= 3 is = 2.0, , x/=2, print ("The x /= 2 is = ",x), x%=3, print ("The x %= 3 is = ",x), x**=2, print ("The x **= 2 is = ",x), x//=3, print ("The x //= 3 is = ",x), #Program End, , (v) Conditional operator, Ternary operator is also known as conditional operator that evaluate something based, on a condition being true or false. It simply allows testing a condition in a single line replacing, the multiline if-else making the code compact., , XII Std Computer Science, , Chapter 5.indd 60, , 60, , 20-02-2019 15:19:40
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The Syntax conditional operator is,, Variable Name = [on_true] if [Test expression] else [on_false], , Example :, min= 50 if 49<50 else 70 # min = 50, min= 50 if 49>50 else 70 # min = 70, Program 5.5 To test Conditional (Ternary) Operator:, # Program to demonstrate conditional operator, a, b = 30, 20, # Copy value of a in min if a < b else copy b, min = a if a < b else b, print ("The Minimum of A and B is ",min), # End of the Program, Output:, The Minimum of A and B is 20, , 5.7.4 Delimiters, Python uses the symbols and symbol combinations as delimiters in expressions, lists,, dictionaries and strings. Following are the delimiters., (, , ), , [, , ], , {, , }, , ,, , :, , ., , ‘, , =, , ;, , +=, , -=, , *=, , /=, , //=, , %=, , &=, , |=, , ^=, , >>=, , <<=, , **=, , 5.7.5 Literals, Literal is a raw data given in a variable or constant. In Python, there are various types, of literals., 1), 2), 3), , Numeric, String, Boolean, , (i) Numeric Literals, Numeric Literals consists of digits and are immutable (unchangeable). Numeric literals, can belong to 3 different numerical types Integer, Float and Complex., 61, , Chapter 5.indd 61, , Python – Variables and Operators, , 20-02-2019 15:19:40
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Program 5.6 : To demonstrate Numeric literals, # Program to demonstrate Numeric Literals, a = 0b1010 , #Binary Literals, b = 100 , #Decimal Literal, c = 0o310 , #Octal Literal, d = 0x12c , #Hexadecimal Literal, print ("Integer Literals :",a,b,c,d), #Float Literal, float_1 = 10.5, float_2 = 1.5e2, print ("Float Literals :",float_1,float_2), #Complex Literal, x = 1 + 3.14 j, print ("Complex Literals :", x), Print ("x = ", x , "Imaginary part of x = ", x.imag, "Real part of x = ", x.real), #End of the Program, Output:, Integer Literals : 10 100 200 300, Float Literals : 10.5 150.0, Complex Literals :, x = (1.3.14) Imaginary part of x = 3.14 Real part of 9 x = 1.0, , (ii) String Literals, In Python a string literal is a sequence of characters surrounded by quotes. Python, supports single, double and triple quotes for a string. A character literal is a single character, surrounded by single or double quotes. The value with triple-quote "' '" is used to give multiline string literal., Program 5.7 To test String Literals, # Demo Program to test String Literals, strings = "This is Python", char = "C", multiline_str = "'This is a multiline string with more than one line code."', print (strings), print (char), print (multiline_str), # End of the Program, Output:, This is Python, C, This is a multiline string with more than one line code., XII Std Computer Science, , Chapter 5.indd 62, , 62, , 20-02-2019 15:19:41
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(iii) Boolean Literals, A Boolean literal can have any of the two values: True or False., Program 5.8 To test Boolean Literals:, # Demo Program to test String Literals, boolean_1 = True, boolean_2 = False, print ("Demo Program for Boolean Literals"), print ("Boolean Value1 :",boolean_1), print ("Boolean Value2 :",boolean_2), # End of the Program, Output:, Demo Program for Boolean Literals, Boolean Value1 : True, Boolean Value2 : False, , (iv) Escape Sequences, In Python strings, the backslash "\" is a special character, also called the "escape", character. It is used in representing certain whitespace characters: "\t" is a tab, "\n" is a, newline, and "\r" is a carriage return. For example to print the message "It's raining", the, Python command is, >>> print ("It\'s rainning"), It's rainning, Python supports the following escape sequence characters., Escape sequence, character, , Description, , Example, , Output, , \\, , Backslash, , >>> print("\\test"), , \test, , \’, , Single-quote, , >>> print("Doesn\'t"), , Doesn't, , \”, , Double-quote, , >>> print("\"Python\""), , "Python", , \n, , New line, , print("Python","\n","Lang.."), , Python Lang.., , \t, , Tab, , print("Python","\t","Lang.."), , Python Lang.., , 5.8 Python Data types, All data values in Python are objects and each object or value has type. Python has Builtin or Fundamental data types such as Number, String, Boolean, tuples, lists and dictionaries., 63, , Chapter 5.indd 63, , Python – Variables and Operators, , 20-02-2019 15:19:41
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5.8.1 Number Data type, The built-in number objects in Python supports integers, floating point numbers and, complex numbers., Integer Data can be decimal, octal or hexadecimal. Octal integer use O (both upper, and lower case) to denote octal digits and hexadecimal integer use OX (both upper and lower, case) and L (only upper case) to denote long integer., , Example :, # Decimal integers, # Octal integers, # Hexadecimal integers, # Long decimal integers, , 102, 4567, 567 , O102, o876, O432 , OX102, oX876, OX432, 34L, 523L , , A floating point data is represented by a sequence of decimal digits that includes a, decimal point. An Exponent data contains decimal digit part, decimal point, exponent part, followed by one or more digits., , Example :, 123.34, 456.23, 156.23 , , # Floating point data, , 12.E04, 24.e04 , , # Exponent data, , Complex number is made up of two floating point values, one each for the real and, imaginary parts., , 5.8.2 Boolean Data type, A Boolean data can have any of the two values: True or False., , Example :, Bool_var1=True, Bool_var2=False, , 5.8.3 String Data type, String data can be enclosed with single quote or double quote or triple quote., , Example :, Char_data = ‘A’, String_data= "Computer Science", Multiline_data= ”””String data can be enclosed with single quote or, double quote or triple quote.”””, XII Std Computer Science, , Chapter 5.indd 64, , 64, , 20-02-2019 15:19:41
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Points to remember:, •, •, •, •, •, , Python is a general purpose programming language created by Guido Van Rossum., Python shell can be used in two ways, viz., Interactive mode and Script mode., Python uses whitespace (spaces and tabs) to define program blocks, Whitespace separation is necessary between tokens, identifiers or keywords., A Program needs to interact with end user to accomplish the desired task, this is done, using Input-Output facility., • Python breaks each logical line into a sequence of elementary lexical components, known as Tokens., • Keywords are special words that are used by Python interpreter to recognize the, structure of program., , Evaluation, Part - I, Choose the best answer, , (1 Marks), , 1. Who developed Python ?, A) Ritche, , B) Guido Van Rossum, , C) Bill Gates, , D) Sunder Pitchai, , 2. The Python prompt indicates that Interpreter is ready to accept instruction., A) >>>, , B) <<<, , C) #, , D) <<, , 3. Which of the following shortcut is used to create new Python Program ?, A) Ctrl + C, , B) Ctrl + F, , C) Ctrl + B, , D) Ctrl + N, , 4. Which of the following character is used to give comments in Python Program ?, A) #, , B) &, , C) @, , D) $, , 5. This symbol is used to print more than one item on a single line., A) Semicolon(;), , B) Dollor($), , C) comma(,), , D) Colon(:), , 6. Which of the following is not a token ?, A) Interpreter, , B) Identifiers, , C) Keyword, , D) Operators, , 65, , Chapter 5.indd 65, , Python – Variables and Operators, , 20-02-2019 15:19:41
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7. Which of the following is not a Keyword in Python ?, A) break, , B) while, , C) continue, , D) operators, , 8. Which operator is also called as Comparative operator?, A) Arithmetic, , B) Relational, , C) Logical, , D) Assignment, , 9. Which of the following is not Logical operator?, A) and, , B) or, , C) not, , D) Assignment, , 10. Which operator is also called as Conditional operator?, A) Ternary, , B) Relational, , C) Logical, , D) Assignment, Part - II, , Answer the following questions :, , (2 Marks), , 1. What are the different modes that can be used to test Python Program ?, 2. Write short notes on Tokens., 3. What are the different operators that can be used in Python ?, 4. What is a literal? Explain the types of literals ?, 5. Write short notes on Exponent data?, Part - III, (3 Marks), , Answer the following questions :, 1. Write short notes on Arithmetic operator with examples., 2. What are the assignment operators that can be used in Python?, 3. Explain Ternary operator with examples., 4. Write short notes on Escape sequences with examples., 5. What are string literals? Explain., Part - IV, , (5 Marks), , Answer the following questions :, 1. Describe in detail the procedure Script mode programming., 2. Explain input() and print() functions with examples., 3. Discuss in detail about Tokens in Python, XII Std Computer Science, , Chapter 5.indd 66, , 66, , 20-02-2019 15:19:41
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Unit, , II, , CHAPTER 6, CONTROL STRUCTURES, , Learning Objectives, After studying this lesson, students will be able to:, • To gain knowledge on the various flow of control in Python language., • To learn through the syntax how to use conditional construct to improve the efficiency of, the program flow., • To apply iteration structures to develop code to repeat the program segment for specific, number of times or till the condition is satisfied., , 6.1, , Introduction, , Programs may contain set of statements. These statements are the executable segments, that yield the result. In general, statements are executed sequentially, that is the statements, are executed one after another. There may be situations in our real life programming where, we need to skip a segment or set of statements and execute another segment based on the test, of a condition. This is called alternative or branching. Also, we may need to execute a set of, statements multiple times, called iteration or looping. In this chapter we are to focus on the, various control structures in Python, their syntax and learn how to develop the programs, using them., , 6.2 Control Structures, A program statement that causes a jump of control from one part of the program to, another is called control structure or control statement. As you have already learnt in C++,, these control statements are compound statements used to alter the control flow of the process, or program depending on the state of the process., , 67, , Chapter 6.indd 67, , 20-02-2019 15:20:07
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There are three important control structures, Sequential, Alternative, Branching, , or, , Iterative or Looping, , 6.2.1 Sequential Statement, A sequential statement is composed of a sequence of statements which are executed, one after another. A code to print your name, address and phone number is an example of, sequential statement., , Example 6.1, # Program to print your name and address - example for sequential statement, print ("Hello! This is Shyam"), print ("43, Second Lane, North Car Street, TN"), Output, Hello! This is Shyam, 43, Second Lane, North Car Street, TN, , 6.2.2 Alternative or Branching Statement, In our day-to-day life we need to take various decisions and choose an alternate path, to achieve our goal. May be we would have taken an alternate route to reach our destination, when we find the usual road by which we travel is blocked. This type of decision making is, what we are to learn through alternative or branching statement. Checking whether the given, number is positive or negative, even or odd can all be done using alternative or branching, statement., , Python provides the following types of alternative or branching statements:, •, , Simple if statement, , •, , if..else statement, , •, , if..elif statement, , (i) Simple if statement, Simple if is the simplest of all decision making statements. Condition should be in the, form of relational or logical expression., XII Std Computer Science, , Chapter 6.indd 68, , 68, , 20-02-2019 15:20:07
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Syntax:, if <condition>:, , statements-block1, In the above syntax if the condition is true statements - block 1 will be executed., , Example 6.2, # Program to check the age and print whether eligible for voting, x=int (input("Enter your age :")), if x>=18:, print ("You are eligible for voting"), Output 1:, Enter your age :34, You are eligible for voting, Output 2:, Enter your age :16, >>>, As you can see in the second execution no output will be printed, only the Python, prompt will be displayed because the program does not check the alternative process when the, condition is failed., , (ii) if..else statement, The if .. else statement provides control to check the true block as well as the false, block. Following is the syntax of ‘if..else’ statement., Syntax:, if <condition>:, statements-block 1, else:, statements-block 2, , 69, , Chapter 6.indd 69, , Control Structures, , 20-02-2019 15:20:07
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Entry, , if condition is, if condition is, condition, true, false, Statement, block -2, , Statement, block -1, , Exit, Fig. 6.1 if..else statement execution, if..else statement thus provides two possibilities and the condition determines which, BLOCK is to be executed., , Example 6.3: #Program to check if the accepted number odd or even, a = int(input("Enter any number :")), if a%2==0:, print (a, " is an even number"), else:, print (a, " is an odd number"), Output 1:, Enter any number :56, 56 is an even number, Output 2:, Enter any number :67, 67 is an odd number, An alternate method to rewrite the above program is also available in Python. The, complete if..else can also written as:, Syntax:, variable = variable1 if condition else variable 2, , XII Std Computer Science, , Chapter 6.indd 70, , 70, , 20-02-2019 15:20:07
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Note, The condition specified in the if is checked, if it is true, the value of variable1 is, stored in variable on the left side of the assignment, otherwise variable2 is taken as the, value., , Example 6.4: #Program to check if the accepted number is odd or even, (using alternate method of if...else), a = int (input("Enter any number :")), x="even" if a%2==0 else "odd", print (a, " is ",x), Output 1:, Enter any number :3, 3 is odd, Output 2:, Enter any number :22, 22 is even, , (iii) Nested if..elif...else statement:, When we need to construct a chain of if statement(s) then ‘elif ’ clause can be used, instead of ‘else’., Syntax:, if <condition-1>:, statements-block 1, elif <condition-2>:, statements-block 2, else:, statements-block n, In the syntax of if..elif..else mentioned above, condition-1 is tested if it is true then, statements-block1 is executed, otherwise the control checks condition-2, if it is true statementsblock2 is executed and even if it fails statements-block n mentioned in else part is executed., , 71, , Chapter 6.indd 71, , Control Structures, , 20-02-2019 15:20:07
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Test, false, Expression, of if, , True, Body of if, , Test, false, Expression, of elif, True, , Body of elif, , Body of else, , Fig 6.2 if..elif..else statement execution, ‘elif ’ clause combines if..else-if..else statements to one if..elif…else. ‘elif ’ can be, considered to be abbreviation of ‘else if ’. In an ‘if ’ statement there is no limit of ‘elif ’ clause, that can be used, but an ‘else’ clause if used should be placed at the end., Note, if..elif..else statement is similar to nested if statement which you have learnt in C++., , XII Std Computer Science, , Chapter 6.indd 72, , 72, , 20-02-2019 15:20:07
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Example 6.5: #Program to illustrate the use of nested if statement, Average, >=80 and above, >=70 and <80, >=60 and <70, >=50 and <60, Otherwise, , Grade, A, B, C, D, E, , m1=int (input(“Enter mark in first subject : ”)), m2=int (input(“Enter mark in second subject : ”)), avg= (m1+m2)/2, if avg>=80:, print (“Grade : A”), elif avg>=70 and avg<80:, print (“Grade : B”), elif avg>=60 and avg<70:, print (“Grade : C”), elif avg>=50 and avg<60:, print (“Grade : D”), else:, print (“Grade : E”), , Output 1:, , Enter mark in first subject : 34, Enter mark in second subject : 78, Grade : D, , Output 2 :, , Enter mark in first subject : 67, , Note, The two blocks of code in our example of if-statement are both indented four, spaces, which is a typical amount of indentation for Python. In most other programming, languages, indentation is used only to help make the code look pretty. But in Python, it, is required to indicate to which block of code the statement belongs to., , 73, , Chapter 6.indd 73, , Control Structures, , 20-02-2019 15:20:08
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Example 6.5a: #Program to illustrate the use of ‘in’ and ‘not in’ in if statement, ch=input (“Enter a character :”), # to check if the letter is vowel, if ch in (‘a’, ‘A’, ‘e’, ‘E’, ‘i’, ‘I’, ‘o’, ‘O’, ‘u’, ‘U’):, print (ch,’ is a vowel’), # to check if the letter typed is not ‘a’ or ‘b’ or ‘c’, if ch not in (‘a’, ’b’, ’c’):, print (ch,’ the letter is not a/b/c’), , Output 1:, Enter a character :e, e is a vowel, , Output 2:, Enter a character :x, x the letter is not a/b/c, , 6.2.3. Iteration or Looping constructs, Iteration or loop are used in situation when the user need to execute a block of code, several of times or till the condition is satisfied. A loop statement allows to execute a statement, or group of statements multiple times., , Condition, True, Statement 1, Statement 2, ..., Statementn, , False, , else, Statement 1, Statement 2, ..., Statementn, Further, Statements, of Program, , Fig 6.3 Diagram to illustrate how looping construct gets executed, , Python provides two types of looping constructs:, •, , while loop, , •, , for loop, , XII Std Computer Science, , Chapter 6.indd 74, , 74, , 20-02-2019 15:20:08
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(i) while loop, The syntax of while loop in Python has the following syntax:, Syntax:, while <condition>:, statements block 1, [else:, statements block2], , while Expression:, Statement (s), Condition, if conditions is true, Conditional Code, , if condition is, false, , Fig 6.4 while loop execution, In the while loop, the condition is any valid Boolean expression returning True or, False. The else part of while is optional part of while. The statements block1 is kept executed, till the condition is True. If the else part is written, it is executed when the condition is tested, False. Recall while loop belongs to entry check loop type, that is it is not executed even once if, the condition is tested False in the beginning., , Example 6.6: program to illustrate the use of while loop - to print all numbers, from 10 to 15, i=10, while (i<=15):, print (i,end='\t'), i=i+1, , # intializing part of the control variable, # test condition, # statements - block 1, # Updation of the control variable, , Output:, 10 11 12 13 14 15, , 75, , Chapter 6.indd 75, , Control Structures, , 20-02-2019 15:20:08
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Note, That the control variable is i, which is initialized to 10, the condition is tested, i<=15, if true value of i gets printed, then the control variable i gets updated as i=i+1 (this, can also be written as i +=1 using shorthand assignment operator). When i becomes 16,, the condition is tested False and this will terminate the loop., , Note, print can have end, sep as parameters. end parameter can be used when we need to give, any escape sequences like ‘\t’ for tab, ‘\n’ for new line and so on. sep as parameter can be, used to specify any special characters like, (comma) ; (semicolon) as separator between, values (Recall the concept which you have learnt in previous chapter about the formatting, options in print())., Following is an example for using else part within while loop., , Example 6.7: program to illustrate the use of while loop - with else part, i=10, while (i<=15):, print (i,end='\t'), i=i+1, else:, print ("\nValue of i when the loop exit ",i), , # intializing part of the control variable, # test condition, # statements - block 1, # Updation of the control variable, , Output: 1, , 10 11 12 13 14 15, Value of i when the loop exit 16, , (ii) for loop, for loop is the most comfortable loop. It is also an entry check loop. The condition is, checked in the beginning and the body of the loop(statements-block 1) is executed if it is only, True otherwise the loop is not executed., Syntax:, for counter_variable in sequence:, statements-block 1, [else: , # optional block, statements-block 2], The counter_variable mentioned in the syntax is similar to the control variable that we, XII Std Computer Science, , Chapter 6.indd 76, , 76, , 20-02-2019 15:20:08
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used in the for loop of C++ and the sequence refers to the initial, final and increment value., Usually in Python, for loop uses the range() function in the sequence to specify the initial, final, and increment values. range() generates a list of values starting from start till stop-1., The syntax of range() is as follows:, range (start,stop,[step]), Where,, start –, , refers to the initial value, , stop, , –, , refers to the final value, , step, , –, , refers to increment value, this is optional part., , Example 6.8: Examples for range(), range (1,30,1), range (2,30,2), range (30,3,-3), range (20), , will start the range of values from 1 and end at 29, will start the range of values from 2 and end at 28, - will start the range of values from 30 and end at 6, will consider this value 20 as the end value(or upper limit) and starts the, range count from 0 to 19 (remember always range() will work till stop -1, value only), for each item, in sequence, , Last item, reached?, , Yes, , No, Body of for, Exit loop, Fig 6.5 for loop execution, , 77, , Chapter 6.indd 77, , Control Structures, , 20-02-2019 15:20:08
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Example 6.9: #program to illustrate the use of for loop - to print single, digit even number, for i in range (2,10,2):, print (i, end=' '), , Output:, 2468, , Following is an illustration using else part in for loop, Example 6.10 : #program to illustrate the use of for loop - to print single, digit even number with else part, for i in range(2,10,2):, print (i,end=' '), else:, print ("\nEnd of the loop"), , Output:, , 2468, End of the loop, , Note, In Python, indentation is important in loop and other control statements. Indentation, only creates blocks and sub-blocks like how we create blocks within a set of { } in languages, like C, C++ etc., Here is another program which illustrates the use of range() to find the sum of numbers, 1 to 100, , Example 6.11: # program to calculate the sum of numbers 1 to 100, n = 100, sum = 0, for counter in range(1,n+1):, sum = sum + counter, print("Sum of 1 until %d: %d" % (n,sum)), , Output:, , Sum of 1 until 100: 5050, In the above code, n is initialized to 100, sum is initialized to 0, the for loop, starts executing from 1, for every iteration the value of sum is added with the value, of counter variable and stored in sum. Note that the for loop will iterate from 1 till, the upper limit -1 (ie. Value of n is set as 100, so this loop will iterate for values from, 1 to 99 only, that is the reason why we have set the upper limit as n+1), , XII Std Computer Science, , Chapter 6.indd 78, , 78, , 20-02-2019 15:20:08
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Note, range () can also take values from string, list, dictionary etc. which will be dealt, in the later chapters., Following is an example to illustrate the use of string in range(), , Example 6.12: program to illustrate the use of string in range() of for loop, for word in 'Computer':, print (word,end=' '), else:, print ("\nEnd of the loop"), , Output, Computer, End of the loop, , (iii) Nested loop structure, A loop placed within another loop is called as nested loop structure. One can place a, while within another while; for within another for; for within while and while within for to, construct such nested loops., Following is an example to illustrate the use of for loop to print the following pattern, 1, 1, , 2, , 1, , 2, , 3, , 1, , 2, , 3, , 4, , 1, , 2, , 3, , 4, , 5, , Example 6.13: program to illustrate the use nested loop -for within while loop, i=1, while (i<=6):, for j in range (1,i):, print (j,end='\t'), print (end='\n'), i +=1, , 79, , Chapter 6.indd 79, , Control Structures, , 20-02-2019 15:20:08
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Output:, 1, 1, , 2, , 1, , 2 3, , 1, , 2, , 3, , 4, , 1, , 2, , 3, , 4, , 5, , 6.2.4 Jump Statements in Python, The jump statement in Python, is used to unconditionally transfer the control from one, part of the program to another. There are three keywords to achieve jump statements in Python, : break, continue, pass. The following flowchart illustrates the use of break and continue., , Condition, True, Statement 1, ..., break, ..., continue, ..., Statementn, , False, , else, Statement 1, Statement 2, ..., Statementn, Further, Statements, of Program, , Fig 6.6 Use of break, continue statement in loop structure, , (i) break statement, The break statement terminates the loop containing it. Control of the program flows to, the statement immediately after the body of the loop., A while or for loop will iterate till the condition is tested false, but one can even transfer, the control out of the loop (terminate) with help of break statement. When the break statement, is executed, the control flow of the program comes out of the loop and starts executing the, segment of code after the loop structure., If break statement is inside a nested loop (loop inside another loop), break will, terminate the innermost loop., XII Std Computer Science, , Chapter 6.indd 80, , 80, , 20-02-2019 15:20:08
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Syntax:, break, Enter loop, false, , Condition, true, break?, , yes, Exit loop, , no, Remaining body of loop, , Fig 6.7 Working of break statement, The working of break statement in for loop and while loop is shown below., for var in sequence:, if condition:, break, #code inside for loop, #code outside for loop, while test expression:, #code inside while loop, if condition:, break, #code inside while loop, #code outside while loop, , 81, , Chapter 6.indd 81, , Control Structures, , 20-02-2019 15:20:08
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Example 6.14: Program to illustrate the use of break statement inside, for loop, for word in “Jump Statement”:, if word = = “e”:, break, print (word, end= ' '), , Output:, Jump Stat, The above program will repeat the iteration with the given “Jump Statement” as string., Each letter of the given string sequence is tested till the letter ‘e’ is encountered, when it is, encountered the control is transferred outside the loop block or it terminates. As shown in the, output, it is displayed till the letter ‘e’ is checked after which the loop gets terminated., One has to note an important point here is that ‘if a loop is left by break, the else part, is not executed’. To explain this lets us enhance the previous program with an ‘else’ part and, see what output will be:, , Example 6.15: Program to illustrate the use of break statement inside, for loop, for word in “Jump Statement”:, if word = = “e”:, break, print (word, end=”), else:, print (“End of the loop”), print (“\n End of the program”), , Output:, Jump Stat, End of the program, Note that the break statement has even skipped the ‘else’ part of the loop and has, transferred the control to the next line following the loop block., , (ii) continue statement, Continue statement unlike the break statement is used to skip the remaining part of a, loop and start with next iteration., , XII Std Computer Science, , Chapter 6.indd 82, , 82, , 20-02-2019 15:20:08
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Syntax:, continue, Enter loop, Test, Expression, of loop, , false, , true, yes, , continue?, Exit loop, , no, Remaining body of loop, , Fig 6.8 Working of continue statement, The working of continue statement in for and while loop is shown below., for var in sequence:, # code inside for loop, if condition:, continue, #code inside for loop, #code outside for loop, while test expression:, #code inside while loop, if condition:, continue, #code inside while loop, #code outside while loop, , 83, , Chapter 6.indd 83, , Control Structures, , 20-02-2019 15:20:08
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Example 6.16: Program to illustrate the use of continue statement inside, for loop, for word in “Jump Statement”:, if word = = “e”:, continue, , , print (word, end=”), , print (“\n End of the program”), , Output:, Jump Statement, End of the program, The above program is same as the program we had written for ‘break’ statement except, that we have replaced it with ‘continue’. As you can see in the output except the letter ‘e’ all the, other letters get printed., , (iii) pass statement, pass statement in Python programming is a null statement. pass statement when, executed by the interpreter it is completely ignored. Nothing happens when pass is executed,, it results in no operation., pass statement can be used in ‘if ’ clause as well as within loop construct, when you do, not want any statements or commands within that block to be executed., Syntax:, pass, , Example 6.17: Program to illustrate the use of pass statement, a=int (input(“Enter any number :”)), if (a==0):, pass, else:, print (“non zero value is accepted”), , Output:, , Enter any number :3, non zero value is accepted, When the above code is executed if the input value is 0 (zero), then no action will be performed, for all the other input values the, output will be as follows:, , XII Std Computer Science, , Chapter 6.indd 84, , 84, , 20-02-2019 15:20:08
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Note, pass statement is generally used as a placeholder. When we have a loop or function, that is to be implemented in the future and not now, we cannot develop such functions, or loops with empty body segment because the interpreter would raise an error. So, to, avoid this we can use pass statement to construct a body that does nothing., , Example 6.18: Program to illustrate the use of pass statement in for loop, for val in “Computer”:, pass, print (“End of the loop, loop structure will be built in future”), , Output:, End of the loop, loop structure will be built in future., , Points to remember:, • Programs consists of statements which are executed in sequence, to alter the, flow we use control statements., • A program statement that causes a jump of control from one part of the, program to another is called control structure or control statement., • Three types of flow of control are, o Sequencing, o Branching or Alternative, o Iteration, • In Python, branching is done using various forms of ‘if ’ structures., • Indentation plays a vital role in Python programming, it is the indentation, that group statements no need to use {}., • Python Interpreter will throw error for all indentation errors., • To accept input at runtime, earlier versions of Python supported raw_input(),, latest versions support input()., • print() supports the use of escape sequence to format the output to the user’s, choice., • range() is used to supply a range of values in for loop., • break, continue, pass act as jump statements in Python., • pass statement is a null statement, it is generally used as a place holder., , 85, , Chapter 6.indd 85, , Control Structures, , 20-02-2019 15:20:08
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Hands on Experience, 1., , Write a program to check whether the given character is a vowel or not., , 2., , Using if..else..elif statement check smallest of three numbers., , 3., , Write a program to check if a number is Positive, Negative or zero., , 4., , Write a program to display Fibonacci series 0 1 1 2 3 4 5…… (upto n terms), , 5., , Write a program to display sum of natural numbers, upto n., , 6., , Write a program to check if the given number is a palindrome or not., , 7., , Write a program to print the following pattern, , 8., , * * * * *, * * * *, * * *, * *, *, Write a program to check if the year is leap year or not., , Evaluation, Part - I, Choose the best answer, 1., , 2., , 3., , 4., , How many important control structures are there in Python?, A) 3, , B) 4, , C) 5, , D) 6, , elif can be considered to be abbreviation of, A) nested if, , B) if..else, , C) else if, , D) if..elif, , What plays a vital role in Python programming?, A) Statements, , B) Control, , C) Structure, , D) Indentation, , Which statement is generally used as a placeholder?, A) continue, , B) break, , C) pass, , D) goto, , XII Std Computer Science, , Chapter 6.indd 86, , 1 Marks, , 86, , 20-02-2019 15:20:08
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5., , The condition in the if statement should be in the form of, A) Arithmetic or Relational expression, B) Arithmetic or Logical expression, C) Relational or Logical expression, D) Arithmetic, , 6., , 7., , Which is the most comfortable loop?, A) do..while, , B) while, , C) for, , D) if..elif, , What is the output of the following snippet?, i=1, while True:, , , , if i%3 ==0:, , break, print(i,end=''), i +=1, , 8., , A) 12, , B) 123, , C) 1234, , D) 124, , What is the output of the following snippet?, T=1, , while T:, print(True), break, , 9., , A) False, , B) True, , C) 0, , D) no output, , Which amongst this is not a jump statement ?, A) for, , B) goto, , C) continue, , D) break, , 10. Which punctuation should be used in the blank?, if <condition>_, statements-block 1, else:, statements-block 2, A) ;, , B) :, , C) ::, , D) !, 87, , Chapter 6.indd 87, , Control Structures, , 20-02-2019 15:20:08
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Part -II, , Answer the following questions, , 2 Marks, , 1., , List the control structures in Python., , 2., , Write note on break statement., , 3., , Write is the syntax of if..else statement, , 4., , Define control structure., , 5., , Write note on range () in loop, Part -III, , Answer the following questions, 1., , 3 Marks, , Write a program to display, A, A B, A B C, A B C D, A B C D E, , 2., , Write note on if..else structure., , 3., , Using if..else..elif statement write a suitable program to display largest of 3 numbers., , 4., , Write the syntax of while loop., , 5., , List the differences between break and continue statements., Part -IV, , Answer the following questions, 1., , Write a detail note on for loop, , 2., , Write a detail note on if..else..elif statement with suitable example., , 3., , Write a program to display all 3 digit odd numbers., , 4., , Write a program to display multiplication table for a given number., , XII Std Computer Science, , Chapter 6.indd 88, , 5 Marks, , 88, , 20-02-2019 15:20:09
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Unit, , II, , CHAPTER 7, PYTHON FUNCTIONS, , Main advantages of functions are, , Learning Objectives, After studying this chapter, students will be, able to:, • Understand the concept of function and, their types., , •, , It avoids repetition and makes high degree, of code reusing., , •, , It provides better modularity for your, application., Note, Functions are nothing but a group, of related statements that perform a, specific task., , • Know the difference between User, defined and Built in functions., • Know how to call a function., • Understand the function arguments., , 7.1.1 Types of Functions, , • Know Anonymous functions., , Basically, we can divide functions, into the following types:, , • Know Mathematical and some String, functions., , 7.1, , User-defined Functions, , 1, , Built-in Functions, , 2, , Introduction, , Lambda Functions, , 3, , Functions are named blocks of code, that are designed to do specific job. When, you want to perform a particular task that, you have defined in a function, you call, the name of the function responsible for it., If you need to perform that task multiple, times throughout your program, you don’t, need to type all the code for the same task, again and again; you just call the function, dedicated to handling that task, and the, call tells Python to run the code inside the, function. You’ll find that using functions, makes your programs easier to write, read,, test, and fix errors., , 4, , Recursion Functions, , Figure – 7.1 – Types of Python Functions, Functions, , Description, , User-defined, functions, , Functions defined by, the users themselves., , Built-in, functions, , Functions that are, inbuilt with in Python., , Lambda, functions, , Functions that are, anonymous un-named, function., , 89, , Chapter 7.indd 89, , 20-02-2019 15:20:32
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Recursion, functions, , • Any input parameters or arguments, should be placed within these, parentheses when you define a function., , Functions that calls, itself is known as, recursive., , Table – 7.1 – Python Functions and it's, Description, , • The code block always comes after a, colon (:) and is indented., , Defining Functions, , • The statement “return [expression]”, exits a function, optionally passing back, an expression to the caller. A “return”, with no arguments is the same as return, None., , 7.2, , Functions must be defined, to create, and use certain functionality. There are, many built-in functions that comes with the, language python (for instance, the print(), function), but you can also define your own, function. When defining functions there are, multiple things that need to be noted;, , Note, Python keywords should not be used, as function name., , • Function blocks begin with the keyword, “def ” followed by function name and, parenthesis ()., , 7.2.1 Syntax for User defined function, def <function_name ([parameter1, parameter2…] )> :, <Block of Statements>, return <expression / None>, , Note, In the above Syntax, the Text, which is given in square, bracket [] is optional., , Nested Block:, , Block:, , A block within a block is called, nested block. When the first block, statement is indented by a single tab, space, the second block of statement is, indented by double tab spaces., , A block is one or more lines of, code, grouped together so that they, are treated as one big sequence of, statements while execution. In Python,, statements in a block are written with, indentation. Usually, a block begins, when a line is indented (by four, spaces) and all the statements of the, block should be at same indent level., , Here is an example of defining a function;, Do_Something( ):, value =1, , #Assignment Statement, , return value #Return Statement, , XII Std Computer Science, , Chapter 7.indd 90, , 90, , 20-02-2019 15:20:33
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Now let’s check out functions in action so you can visually see how they work within a, program. Here is an example for a simple function to display the given string., , Example:, def hello():, print (“hello - Python”), return, 7.2.2 Advantages of User-defined Functions, 1. Functions help us to divide a program into modules. This makes the code easier to, manage., 2. It implements code reuse. Every time you need to execute a sequence of statements, all, you need to do is to call the function., 3. Functions, allows us to change functionality easily, and different programmers can work, on different functions., , 7.3 Calling a Function, To call the hello() function from example 7.2-1, you use this code:, When you call the “hello()” function, the program displays the following string as, output:, Output, hello – Python, Alternatively we can call the “hello()” function within the print() function as in the, example given below., , Example:, def hello():, print (“hello - Python”), return, print (hello()), If the return has no argument, “None” will be displayed as the last statement of the, output., The above function will output the following., Output:, hello – Python, None, 91, , Chapter 7.indd 91, , Python Functions, , 20-02-2019 15:20:33
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7.4 Passing Parameters in Functions, Parameters or arguments can be passed to functions, def function_name (parameter(s) separated by comma):, Let us see the use of parameters while defining functions. The parameters that you, place in the parenthesis will be used by the function itself. You can pass all sorts of data to the, functions. Here is an example program that defines a function that helps to pass parameters, into the function., , Example:, # assume w = 3 and h = 5, def area(w,h):, , , return w * h, , print (area (3,5)), The above code assigns the width and height values to the parameters w and h. These, parameters are used in the creation of the function “area”. When you call the above function,, it returns the product of width and height as output., The value of 3 and 5 are passed to w and h respectively, the function will return 15 as, output., , We often use the terms parameters and arguments interchangeably. However, there, is a slight difference between them. Parameters are the variables used in the function, definition whereas arguments are the values we pass to the function parameters, , 7.5, , Function Arguments, , Arguments are used to call a function and there are primarily 4 types of functions that, one can use: Required arguments, Keyword arguments, Default arguments and Variable-length, arguments., , XII Std Computer Science, , Chapter 7.indd 92, , 92, , 20-02-2019 15:20:33
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Function Arguments, , 1, , Required arguments, , 2, , Keyword arguments, , 3, , Default arguments, , 4, , Variable-length arguments, , 7.5.1 Required Arguments, “Required Arguments” are the arguments passed to a function in correct positional, order. Here, the number of arguments in the function call should match exactly with the, function definition. You need atleast one parameter to prevent syntax errors to get the required, output., , Example :, def printstring(str):, print ("Example - Required arguments "), print (str), return, # Now you can call printstring() function, printstring(), When the above code is executed, it produces the following error., Traceback (most recent call last):, File "Req-arg.py", line 10, in <module>, printstring(), TypeError: printstring() missing 1 required positional argument: 'str', Instead of printstring() in the above code if we use printstring (“Welcome”) then the, output is, Output:, Example - Required arguments, Welcome, 93, , Chapter 7.indd 93, , Python Functions, , 20-02-2019 15:20:33
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7.5.2 Keyword Arguments, Keyword arguments will invoke the function after the parameters are recognized by, their parameter names. The value of the keyword argument is matched with the parameter, name and so, one can also put arguments in improper order (not in order)., , Example:, def printdata (name):, print (“Example-1 Keyword arguments”), print (“Name :”,name), return, # Now you can call printdata() function, printdata(name = “Gshan”), When the above code is executed, it produces the following output :, Output:, Example-1 Keyword arguments, Name :Gshan, , Example:, def printdata (name):, print (“Example-2 Keyword arguments”), print (“Name :”, name), return, # Now you can call printdata() function, printdata (name1 = “Gshan”), When the above code is executed, it produces the following result :, TypeError: printdata() got an unexpected keyword argument 'name1', , Example:, def printdata (name, age):, print ("Example-3 Keyword arguments"), print ("Name :",name), print ("Age :",age), return, # Now you can call printdata() function, printdata (age=25, name="Gshan"), , XII Std Computer Science, , Chapter 7.indd 94, , 94, , 20-02-2019 15:20:33
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When the above code is executed, it produces the following result:, Output:, Example-3 Keyword arguments, Name : Gshan, Age : 25, Note, In the above program the parameters orders are changed, , 7.5.3 Default Arguments, In Python the default argument is an argument that takes a default value if no value, is provided in the function call. The following example uses default arguments, that prints, default salary when no argument is passed., , Example:, def printinfo( name, salary = 3500):, print (“Name: “, name), print (“Salary: “, salary), return, printinfo(“Mani”), When the above code is executed, it produces the following output, Output:, Name: Mani, Salary: 3500, When the above code is changed as print info(“Ram”,2000) it produces the following, output:, Output:, Name: Ram, Salary: 2000, In the above code, the value 2000 is passed to the argument salary, the default value, already assigned for salary is simply ignored., , 95, , Chapter 7.indd 95, , Python Functions, , 20-02-2019 15:20:33
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7.5.4 Variable-Length Arguments, In some instances you might need to pass more arguments than have already been, specified. Going back to the function to redefine it can be a tedious process. Variable-Length, arguments can be used instead. These are not specified in the function’s definition and an, asterisk (*) is used to define such arguments., Lets see what happens when we pass more than 3 arguments in the sum() function., , Example:, def sum(x,y,z):, print("sum of three nos :",x+y+z), sum(5,10,15,20,25), When the above code is executed, it produces the following result :, TypeError: sum() takes 3 positional arguments but 5 were given, , 7.5.4.1 Syntax - Variable-Length Arguments, def function_name(*args):, function_body, return_statement, , Example:, def printnos (*nos):, for n in nos:, print(n), return, # now invoking the printnos() function, print ('Printing two values'), printnos (1,2), print ('Printing three values'), printnos (10,20,30), , Evaluate Yourself, , Output:, Printing two values, 1, 2, Printing three values, 10, 20, 30, , ?, , In the above program change the function name printnos as printnames in all places, wherever it is used and give the appropriate data Ex. printnos (10, 20, 30) as printnames ('mala',, 'kala', 'bala') and see output., XII Std Computer Science, , Chapter 7.indd 96, , 96, , 20-02-2019 15:20:33
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In Variable Length arguments we can pass the arguments using two methods., 1., , Non keyword variable arguments, , 2., , Keyword variable arguments, , Non-keyword variable arguments are called tuples. You will learn more about tuples in, the later chapters. The Program given is an illustration for non keyword variable argument., Note, Keyword variable arguments are beyond the scope of this book., The Python’s print() function is itself an example of such a function which, supports variable length arguments., , 7.6, , Anonymous Functions, , What is anonymous function?, In Python, anonymous function is a function that is defined without a name. While, normal functions are defined using the def keyword, in Python anonymous functions are, defined using the lambda keyword. Hence, anonymous functions are also called as lambda, functions., , What is the use of lambda or anonymous function?, • Lambda function is mostly used for creating small and one-time anonymous function., • Lambda functions are mainly used in combination with the functions like filter(), map(), and reduce()., Note, filter(), map() and reduce() functions are beyond the scope of this book., Lambda function can take any number of arguments and must return one, value in the form of an expression. Lambda function can only access global variables, and variables in its parameter list., , 97, , Chapter 7.indd 97, , Python Functions, , 20-02-2019 15:20:33
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7.6.1 Syntax of Anonymous Functions, The syntax for anonymous functions is as follows:, , Example:, , lambda [argument(s)] :expression, , sum = lambda arg1, arg2: arg1 + arg2, print ('The Sum is :', sum(30,40)), print ('The Sum is :', sum(-30,40)), Output:, The Sum is : 70, The Sum is : 10, , The above lambda function that adds argument arg1 with argument arg2 and stores the, result in the variable sum. The result is displayed using the print()., , 7.7, , The return Statement, , • The return statement causes your function to exit and returns a value to its caller. The, point of functions in general is to take inputs and return something., • The return statement is used when a function is ready to return a value to its caller. So,, only one return statement is executed at run time even though the function contains, multiple return statements., • Any number of 'return' statements are allowed in a function definition but only one of, them is executed at run time., , 7.7.1 Syntax of return, return [expression list ], This statement can contain expression which gets evaluated and the value is returned., If there is no expression in the statement or the return statement itself is not present inside a, function, then the function will return the None object., , XII Std Computer Science, , Chapter 7.indd 98, , 98, , 20-02-2019 15:20:33
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Example :, # return statment, def usr_abs (n):, if n>=0:, return n, else:, return –n, # Now invoking the function, x=int (input(“Enter a number :”), print (usr_abs (x)), Output 1:, Enter a number : 25, 25, Output 2:, Enter a number : -25, 25, , 7.8, , Scope of Variables, , Scope of variable refers to the part of the program, where it is accessible, i.e., area where, you can refer (use) it. We can say that scope holds the current set of variables and their values., We will study two types of scopes - local scope and global scope., 7.8.1 Local Scope, A variable declared inside the function's body or in the local scope is known as local, variable., Rules of local variable, • A variable with local scope can be accessed only within the function/block that it is created, in., • When a variable is created inside the function/block, the variable becomes local to it., • A local variable only exists while the function is executing., • The formate arguments are also local to function., , 99, , Chapter 7.indd 99, , Python Functions, , 20-02-2019 15:20:33
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Example : Create a Local Variable, def loc():, y=0 # local scope, print(y), loc(), Output:, 0, , Example : Accessing local variable outside the scope, def loc():, y = "local", loc(), print(y), When we run the above code, the output shows the following error:, scope., , The above error occurs because we are trying to access a local variable ‘y’ in a global, NameError: name 'y' is not defined, , 7.8.2 Global Scope, A variable, with global scope can be used anywhere in the program. It can be created by, defining a variable outside the scope of any function/block., Rules of global Keyword, The basic rules for global keyword in Python are:, • When we define a variable outside a function, it’s global by default. You don’t have to use, global keyword., • We use global keyword to read and write a global variable inside a function., • Use of global keyword outside a function has no effect, Use of global Keyword, , Example : Accessing global Variable From Inside a Function, c = 1 , # global variable, def add():, print(c), add(), Output:, 1, XII Std Computer Science, , Chapter 7.indd 100, , 100, , 20-02-2019 15:20:33
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Example : Accessing global Variable From Inside a Function, c = 1 , # global variable, def add():, print(c), add(), Output:, 1, , Example : Modifying Global Variable From Inside the Function, c = 1 , # global variable, def add():, c = c + 2 # increment c by 2, print(c), add(), Output:, Unbound Local Error: local variable 'c' referenced before assignment, Note, Without using the global keyword we cannot modify the global variable inside, the function but we can only access the global variable., , Example : C hanging Global Variable From Inside a Function using global, keyword, x = 0 , # global variable, def add():, global x, x = x + 5 , # increment by 2, print ("Inside add() function x value is :", x), add(), print ("In main x value is :", x), Output:, Inside add() function x value is : 5, In main x value is : 5, In the above program, x is defined as a global variable. Inside the add() function, global, keyword is used for x and we increment the variable x by 5. Now We can see the change on the, global variable x outside the function i.e the value of x is 5., 101, , Chapter 7.indd 101, , Python Functions, , 20-02-2019 15:20:33
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7.8.3 Global and local variables, Here, we will show how to use global variables and local variables in the same code., , Example : Using Global and Local variables in same code, x=8 , def loc():, global x, y = "local", x=x*2, print(x), print(y), loc(), , # x is a global variable, , Output:, 16, local, loc()., , In the above program, we declare x as global and y as local variable in the function, , After calling the function loc(), the value of x becomes 16 because we used x=x * 2., After that, we print the value of local variable y i.e. local., , Example : Global variable and Local variable with same name, x=5, def loc():, x = 10, print ("local x:", x), loc(), print ("global x:", x), Output:, local x: 10, global x: 5, In above code, we used same name ‘x’ for both global variable and local variable. We get, different result when we print same variable because the variable is declared in both scopes, i.e., the local scope inside the function loc() and global scope outside the function loc()., The output :- local x: 10, is called local scope of variable., The output:- global x: 5, is called global scope of variable., XII Std Computer Science, , Chapter 7.indd 102, , 102, , 20-02-2019 15:20:33
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7.9 Functions using libraries, 7.9.1 Built-in and Mathematical functions, Function, abs ( ), , ord ( ), , chr ( ), , bin ( ), , Description, , Syntax, , Example, , Returns, an, absolute value, of a number., The argument, may be an abs (x), integer or a, floating point, n u m b e r., , x=20, y=-23.2, print('x = ', abs(x)), print('y = ', abs(y)), , Returns the, ASCII value, for the given, Unicode, character., This function is, inverse of chr(), function., , c= 'a', d= 'A', print ('c = ',ord (c)), print ('A = ',ord (d)), , Output:, x = 20, y = 23.2, , ord (c), , Output:, c = 97, A = 65, , Returns the, Unicode, character for, the given ASCII chr (i), value., This function is, inverse of ord(), function., , c=65, d=43, print (chr (c)), prin t(chr (d)), , Returns a, binary string, prefixed with, “0b” for the, given integer, number., Note: format, () can also be, used instead of, this function., , x=15, y=101, print ('15 in binary : ',bin (x)), print ('101 in binary : ',bin (y)), , Output:, A, +, , bin (i), , Output:, 15 in binary : 0b1111, 101 in binary : 0b1100101, , 103, , Chapter 7.indd 103, , Python Functions, , 20-02-2019 15:20:33
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type ( ), , id ( ), , min ( ), , max ( ), , sum ( ), , Returns the, type of object, for the given, single object., Note: This, function, used with, single object, parameter., , type (object), , Output:, <class 'float'>, <class 'str'>, <class 'bool'>, , id( ) Return, the “identity” of, an object. i.e., the address of, id (object), the object in, memory., Note: the, address of x, and y may, differ in your, system., , x=15, y='a', print ('address of x is :',id (x)), print ('address of y is :',id (y)), , Returns the, minimum value, in a list., min (list), , MyList = [21,76,98,23], , Returns the, maximum, value in a list., , Returns the, sum of values, in a list., , XII Std Computer Science, , Chapter 7.indd 104, , x= 15.2, y= 'a', s= True, print (type (x)), print (type (y)), print (type (s)), , Output:, address of x is : 1357486752, address of y is : 13480736, , print ('Minimum of MyList :', min(MyList)), , Output:, Minimum of MyList : 21, MyList = [21,76,98,23], , print ('Maximum of MyList :', max(MyList)), , Output:, Maximum of MyList : 98, , max (list), , MyList = [21,76,98,23], print ('Sum of MyList :', sum(MyList)), , sum (list), , Output:, Sum of MyList : 218, , 104, , 20-02-2019 15:20:33
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format ( ) Returns the, output based, on the given, format, 1. Binary, format., Outputs the, number in, base 2., 2. Octal, format., Outputs the, number in, base 8., 3. Fixed-point, notation., Displays the, number as a, fixed-point, number., The default, precision, is 6., round ( ), , Returns the, nearest integer, to its input., 1. First, argument, (number), is used to, specify the, value to be, rounded., , x= 14, y= 25, print ('x value in binary :',format(x,'b')), print ('y value in octal :',format(y,'o')), , print('y value in Fixed-point no ',format(y,'f ')), , format (value, [, format_, spec]), , x= 17.9, y= 22.2, z= -18.3, print ('x value is rounded to', round (x)), print ('y value is rounded to', round (y)), print ('z value is rounded to', round (z)), , round, (number, [,ndigits]), , 105, , Chapter 7.indd 105, , Output:, x value in binary : 1110, y value in octal : 31, y value in Fixed-point no : 25.000000, , Python Functions, , 20-02-2019 15:20:33
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pow ( ), , 2. Second, argument, (ndigits), is used to, specify the, number, of decimal, digits, desired after, rounding., , Output:1, x value is rounded to 18, y value is rounded to 22, z value is rounded to -18, n1=17.89, print (round (n1,0)), print (round (n1,1)), print (round (n1,2)), , Returns the, computation of, ab i.e. (a**b ), a raised to the, power of b., , a= 5, b= 2, c= 3.0, print (pow (a,b)), print (pow (a,c)), print (pow (a+b,3)), , Output:2, 18.0, 17.9, 17.89, , pow (a,b), , Output:, 25, 125.0, 343, , Mathematical Functions, Note, Import math module for all mathematical functions., Function, floor ( ), , Description, , Returns the largest integer math.floor (x), less than or equal to x, , XII Std Computer Science, , Chapter 7.indd 106, , Syntax, , Example, x=26.7, y=-26.7, z=-23.2, print (math.floor (x)), print (math.floor (y)), print (math.floor (z)), Output:, 26, -27, -24, , 106, , 20-02-2019 15:20:33
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ceil ( ), , Returns the smallest, integer greater than or, equal to x, , math.ceil (x), , x= 26.7, y= -26.7, z= -23.2, print (math.ceil (x)), print (math.ceil (y)), print (math.ceil (z)), Output:, 27, -26, -23, , sqrt ( ), , Returns the square root, of x, Note: x must be greater, than 0 (zero), , sqrt (x ), , a= 30, b= 49, c= 25.5, print (math.sqrt (a)), print (math.sqrt (b)), print (math.sqrt (c)), Output:, 5.477225575051661, 7.0, 5.049752469181039, , 7.9.2 Composition in functions, What is Composition in functions?, The value returned by a function may be used as an argument for another function in, a nested manner. This is called composition. For example, if we wish to take a numeric value, or an expression as a input from the user, we take the input string from the user using the, function input() and apply eval() function to evaluate its value, for example:, , Example :, # This program explains composition, >>> n1 = eval (input ("Enter a number: ")), Enter a number: 234, >>> n1, 234, >>> n2 = eval (input ("Enter an arithmetic expression: ")), Enter an arithmetic expression: 12.0+13.0 * 2, >>> n2, 38.0, , 7.10 Python recursive functions, When a function calls itself is known as recursion. Recursion works like loop but, sometimes it makes more sense to use recursion than loop. You can convert any loop to, recursion., 107, , Chapter 7.indd 107, , Python Functions, , 20-02-2019 15:20:33
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A recursive function calls itself. Imagine a process would iterate indefinitely if not, stopped by some condition! Such a process is known as infinite iteration. The condition that, is applied in any recursive function is known as base condition. A base condition is must in, every recursive function otherwise it will continue to execute like an infinite loop., Overview of how recursive function works, 1. Recursive function is called by some external code., 2. If the base condition is met then the program gives meaningful output and exits., 3. Otherwise, function does some required processing and then calls itself to continue, recursion., Here is an example of recursive function used to calculate factorial., , Example :, def fact(n):, if n == 0:, return 1, else:, , return n * fact (n-1), print (fact (0)), print (fact (5)), Output:, 1, 120, print(fact (2000)) will give Runtime Error maximum recursion depth exceeded in, comparison. This happens because python stops calling recursive function after, 1000 calls by default. It also allows you to change the limit using sys.setrecursionlimit, (limit_value)., Example:, import sys, sys.setrecursionlimit(3000), def fact(n):, , if n == 0:, return 1, else:, , return n * fact(n-1), print(fact (2000)), , XII Std Computer Science, , Chapter 7.indd 108, , 108, , 20-02-2019 15:20:33
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Points to remember:, • Functions are named blocks of code that are designed to do one specific job., • Types of Functions are User defined, Built-in, lambda and recursion., • Function blocks begin with the keyword “def ” followed by function name and, parenthesis ()., • A “return” with no arguments is the same as return None. Return statement, is optional in python., • In Python, statements in a block should begin with indentation., • A block within a block is called nested block., • Arguments are used to call a function and there are primarily 4 types of, functions that one can use: Required arguments, Keyword arguments, Default, arguments and Variable-length arguments., • Required arguments are the arguments passed to a function in correct, positional order., • Keyword arguments will invoke the function after the parameters are, recognized by their parameter names., • A Python function allows us to give the default values for parameters in the, function definition. We call it as Default argument., • Variable-Length arguments are not specified in the function’s definition and, an asterisk (*) is used to define such arguments., • Anonymous Function is a function that is defined without a name., • Scope of variable refers to the part of the program, where it is accessible, i.e.,, area where you can refer (use) it., • The value returned by a function may be used as an argument for another, function in a nested manner. This is called composition., • A function which calls itself is known as recursion. Recursion works like a, loop but sometimes it makes more sense to use recursion than loop., , 109, , Chapter 7.indd 109, , Python Functions, , 20-02-2019 15:20:34
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Hands on Experience, , 1. Try the following code in the above program, Slno, , code, , Result, , 1, , printinfo(“3500”), , 2, , printinfo(“3500”,”Sri”), , 3, , printinfo(name=”balu”), , 4, , printinfo(“Jose”,1234), , 5, , printinfo(“ ”,salary=1234), , 2. Evaluate the following functions and write the output, Slno, , Function, , 1, , eval(‘25*2-5*4'), , 2, , math.sqrt(abs(-81)), , 3, , math.ceil(3.5+4.6), , 4, , math.floor(3.5+4.6), , Output, , 3. Evaluate the following functions and write the output, Slno, 1, , 1) abs(-25+12.0)), 2) abs(-3.2), , 2, , 1) ord('2'), 2) ord('$'), , 3, , type('s'), , 4, , bin(16), , 5, , 1) chr(13), 2) print(chr(13)), , 6, , 1) round(18.2,1), 2) round(18.2,0), 3) round(0.5100,3), 4) round(0.5120,3), , XII Std Computer Science, , Chapter 7.indd 110, , function, , Output, , 110, , 20-02-2019 15:20:34
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7, , 1) format(66, 'c'), 2) format(10, 'x'), 3) format(10, 'X'), 4) format(0b110, 'd'), 5) format(0xa, 'd'), , 8, , 1) pow(2,-3), 2) pow(2,3.0), 3) pow(2,0), 4) pow((1+2),2), 5) pow(-3,2), 6) pow(2*2,2), , Evaluation, Part - I, Choose the best answer:, 1., , 2., , 3., , 4., , 5., , 6., , (1 Mark), , A named blocks of code that are designed to do one specific job is called as, (a) Loop, , (b) Branching, , (c) Function, , (d) Block, , A Function which calls itself is called as, (a) Built-in, , (b) Recursion, , (c) Lambda, , (d) return, , Which function is called anonymous un-named function, (a) Lambda, , (b) Recursion, , (c) Function, , (d) define, , Which of the following keyword is used to begin the function block?, (a) define, , (b) for, , (c) finally, , (d) def, , Which of the following keyword is used to exit a function block?, (a) define, , (b) return, , (c) finally, , (d) def, , While defining a function which of the following symbol is used., (a) ; (semicolon), , (b) . (dot), , (c) : (colon), , (d) $ (dollar), 111, , Chapter 7.indd 111, , Python Functions, , 20-02-2019 15:20:34
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7., , 8., , In which arguments the correct positional order is passed to a function?, (a) Required, , (b) Keyword, , (c) Default, , (d) Variable-length, , Read the following statement and choose the correct statement(s)., , (I) In Python, you don’t have to mention the specific data types while defining, function., (II) Python keywords can be used as function name., (a) I is correct and II is wrong, (b) Both are correct, (c) I is wrong and II is correct, (d) Both are wrong, 9., , Pick the correct one to execute the given statement successfully., if ____ : print(x, " is a leap year"), (a) x%2=0, , (b) x%4==0, , (c) x/4=0, , (d) x%4=0, , 10. Which of the following keyword is used to define the function testpython(): ?, (a) define, , (b) pass, , (c) def, , (d) while, Part - II, , Answer the following questions:, , (2 Marks), , 1., , What is function?, , 2., , Write the different types of function., , 3., , What are the main advantages of function?, , 4., , What is meant by scope of variable? Mention its types., , 5., , Define global scope., , 6., , What is base condition in recursive function, , 7., , How to set the limit for recursive function? Give an example., , XII Std Computer Science, , Chapter 7.indd 112, , 112, , 20-02-2019 15:20:34
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Part - III, Answer the following questions:, , (3 Marks), , 1., , Write the rules of local variable., , 2., , Write the basic rules for global keyword in python., , 3., , What happens when we modify global variable inside the function?, , 4., , Differentiate ceil() and floor() function?, , 5., , Write a Python code to check whether a given year is leap year or not., , 6., , What is composition in functions?, , 7., , How recursive function works?, , 8., , What are the points to be noted while defining a function?, Part - IV, , Answer the following questions:, , (5 Marks), , 1., , Explain the different types of function with an example., , 2., , Explain the scope of variables with an example., , 3., , Explain the following built-in functions., (a) id(), (b) chr(), (c) round(), (d) type(), (e) pow(), , 4., , Write a Python code to find the L.C.M. of two numbers., , 5., , Explain recursive function with an example., , Reference Books, 1. Python Tutorial book from tutorialspoint.com, 2. Python Programming: A modular approach by Pearson – Sheetal, Taneja, 3. Fundamentals of Python –First Programs by Kenneth A. Lambert, , 113, , Chapter 7.indd 113, , Python Functions, , 20-02-2019 15:20:34
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Unit, , II, , CHAPTER 8, STRINGS AND STRING MANIPULATION, , Learning Objectives, After completion of this chapter, the student will be able to, • Know how to process text., • Understanding various string functions in Python., • Know how to format Strings., • Know about String Slicing., • Know about Strings application in real world., , 8.1 Introduction, String is a data type in python, which is used to handle array of characters. String is, a sequence of Unicode characters that may be a combination of letters, numbers, or special, symbols enclosed within single, double or even triple quotes., , Example, ‘Welcome to learning Python’, “Welcome to learning Python”, ‘‘‘ “Welcome to learning Python” ’’’, In python, strings are immutable, it means, once you define a string, it cannot be, changed during execution., , 8.2 Creating Strings, As we learnt already, a string in Python can be created using single or double or even, triple quotes. String in single quotes cannot hold any other single quoted character in it, because, the compiler will not recognize where to start and end the string. To overcome this problem,, you have to use double quotes. Strings which contains double quotes should be define within, triple quotes. Defining strings within triple quotes also allows creation of multiline strings., , XII Std Computer Science, , Chapter 8.indd 114, , 114, , 20-02-2019 15:20:52
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Example, #A string defined within single quotes, >>> print (‘Greater Chennai Corporation’), Greater Chennai Corporation, #single quoted string defined within single quotes, >>> print ('Greater Chennai Corporation's student'), SyntaxError: invalid syntax, #A string defined within double quotes, >>>print (“Computer Science”), Computer Science, #double quoted string defined within double quotes, >>> print (''' "Computer Science" '''), "Computer Science", #single and double quoted multiline string defined within triple quotes, >>> print (''' "Strings are immutable in 'Python',, , which means you can't make any changes, , once you declared" '''), "Strings are immutable in 'Python',, which means you can't make any changes once you declared", , 8.3 Accessing characters in a String, Once you define a string, python allocate an index value for its each character. These, index values are otherwise called as subscript which are used to access and manipulate the, strings. The subscript can be positive or negative integer numbers., The positive subscript 0 is assigned to the first character and n-1 to the last character,, where n is the number of characters in the string. The negative index assigned from the last, character to the first character in reverse order begins with -1., , Example, String, , S, , C, , H, , O, , O, , L, , Positive subscript, , 0, , 1, , 2, , 3, , 4, , 5, , Negative subscript, , -6, , -5, , -4, , -3, , -2, , -1, , 115, , Chapter 8.indd 115, , Strings and String Manipulation, , 20-02-2019 15:20:52
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Example 1 : Program to access each character with its positive subscript of, a giving string, str1 = input ("Enter a string: "), index=0, for i in str1:, print ("Subscript[",index,"] : ", i), index + = 1, Output, Enter a string: welcome, Subscript [ 0 ] : w, Subscript [ 1 ] : e, Subscript [ 2 ] : l, Subscript [ 3 ] : c, Subscript [ 4 ] : o, Subscript [ 5 ] : m, Subscript [ 6 ] : e, , Example 2 : Program to access each character with its negative subscript of, a giving string, str1 = input ("Enter a string: "), index=-1, while index >= -(len(str1)):, print ("Subscript[",index,"] : " + str1[index]), index += -1, Output, Enter a string: welcome, Subscript [ -1 ] : e, Subscript [ -2 ] : m, Subscript [ -3 ] : o, Subscript [ -4 ] : c, Subscript [ -5 ] : l, Subscript [ -6 ] : e, Subscript [ -7 ] : w, 8.4 Modifying and Deleting Strings, As you already learnt, strings in python are immutable. That means, once you define a, string modifications or deletion is not allowed. If you want to modify the string, a new string, value can be assign to the existing string variable., , XII Std Computer Science, , Chapter 8.indd 116, , 116, , 20-02-2019 15:20:52
Page 123 : Example, >>> str1="How are you", >>> str1[0]="A", Traceback (most recent call last):, , File "<pyshell#1>", line 1, in <module>, str1[0]="A", TypeError: 'str' object does not support item assignment, In the above example, string variable str1 has been assigned with the string “How are, you” in statement 1. In the next statement, we try to update the first character of the string with, character ‘A’. But python will not allow the update and it shows a TypeError., To overcome this problem, you can define a new string value to the existing string, variable. Python completely overwrite new string on the existing string., , Example, >>> str1="How are you", >>> print (str1), How are you, >>> str1="How about you", >>> print (str1), How about you, Usually python does not support any modification in its strings. But, it provides a, function replace() to change all occurrences of a particular character in a string., General formate of replace function:, replace(“char1”, “char2”), The replace function replaces all occurrences of char1 with char2., , Example, >>> str1="How are you", >>> print (str1), How are you, >>> print (str1.replace("o", "e")), Hew are yeu, Similar as modification, python will not allow deleting a particular character in a string., Whereas you can remove entire string variable using del command., 117, , Chapter 8.indd 117, , Strings and String Manipulation, , 20-02-2019 15:20:53
Page 124 : Example 3: Code lines to delete a particular character in a string:, >>> str1="How are you", >>> del str1[2], Traceback (most recent call last):, File "<pyshell#7>", line 1, in <module>, del str1[2], TypeError: 'str' object doesn't support item deletion, , Example 4: Code lines to delete a string variable, >>> str1="How about you", >>> print (str1), How about you, >>> del str1, >>> print (str1), Traceback (most recent call last):, File "<pyshell#14>", line 1, in <module>, print (str1), NameError: name 'str1' is not defined, 8.5 String Operators, Python provides the following operators for string operations. These operators are, useful to manipulate string., (i) Concatenation (+), Joining of two or more strings is called as Concatenation. The plus (+) operator is used, to concatenate strings in python., Example, >>> "welcome" + "Python", 'welcomePython', (ii) Append (+ =), Adding more strings at the end of an existing string is known as append. The operator, += is used to append a new string with an existing string., Example, >>> str1="Welcome to ", XII Std Computer Science, , Chapter 8.indd 118, , 118, , 20-02-2019 15:20:53
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>>> str1+="Learn Python", >>> print (str1), Welcome to Learn Python, (iii) Repeating (*), The multiplication operator (*) is used to display a string in multiple number of times., Example, >>> str1="Welcome ", >>> print (str1*4), , , Welcome Welcome Welcome Welcome, , (iv) String slicing, Slice is a substring of a main string. A substring can be taken from the original string, by using [ ] operator and index or subscript values. Thus, [ ] is also known as slicing operator., Using slice operator, you have to slice one or more substrings from a main string., General format of slice operation:, str[start:end], Where start is the beginning index and end is the last index value of a character in the, string. Python takes the end value less than one from the actual index specified. For example,, if you want to slice first 4 characters from a string, you have to specify it as 0 to 5. Because,, python consider only the end value as n-1., Example I : slice a single character from a string, >>> str1="THIRUKKURAL", >>> print (str1[0]), T, Example II : slice a substring from index 0 to 4, >>> print (str1[0:5]), THIRU, Example III : slice a substring using index 0 to 4 but without specifying the beginning, index., >>> print (str1[:5]), THIRU, Example IV : slice a substring using index 0 to 4 but without specifying the end index., >>> print (str1[6:]), KURAL, 119, , Chapter 8.indd 119, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Example V : Program to slice substrings using for loop, str1="COMPUTER", index=0, for i in str1:, print (str1[:index+1]), index+=1, Output, C, CO, COM, COMP, COMPU, COMPUT, COMPUTE, COMPUTER, (v) Stride when slicing string, When the slicing operation, you can specify a third argument as the stride, which refers, to the number of characters to move forward after the first character is retrieved from the, string. The default value of stride is 1., , Example, >>> str1 = "Welcome to learn Python", >>> print (str1[10:16]), , learn, >>> print (str1[10:16:4]), r, >>> print (str1[10:16:2]), , er, >>> print (str1[::3]), Wceoenyo, Note: Remember that, python takes the last value as n-1, You can also use negative value as stride (third argument). If you specify a negative, value, it prints in reverse order., , XII Std Computer Science, , Chapter 8.indd 120, , 120, , 20-02-2019 15:20:53
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Example, >>> str1 = "Welcome to learn Python", >>> print(str1[::-2]), nhy re teolW, 8.6 String Formatting Operators, The string formatting operator is one of the most exciting feature of python. The, formatting operator % is used to construct strings, replacing parts of the strings with the data, stored in variables., Syntax:, (“String to be display with %val1 and %val2” %(val1, val2)), , Example, name = "Rajarajan", mark = 98, print ("Name: %s and Marks: %d" %(name,mark)), Output, Name: Rajarajan and Marks: 98, 8.7 Formatting characters, Format characters, , USAGE, , %c, , Character, , %d (or) %i, , Signed decimal integer, , %s, , String, , %u, , Unsigned decimal integer, , %o, , Octal integer, , %x or %X, , Hexadecimal integer (lower case x refers a-f; upper case X refers, A-F), , %e or %E, , Exponential notation, , %f, , Floating point numbers, , %g or %G, , Short numbers in floating point or exponential notation., , 121, , Chapter 8.indd 121, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Escape sequence in python, Escape sequences starts with a backslash and it can be interpreted differently. When, you have use single quote to represent a string, all the single quotes inside the string must be, escaped. Similar is the case with double quotes., , Example, # String within triple quotes to display a string with single quote, >>> print ('''They said, "What's there?"'''), They said, "What's there?", # String within single quotes to display a string with single quote using escape sequence, >>> print ('They said, "What\'s there?"'), They said, "What's there?", # String within double quotes to display a string with single quote using escape sequence, >>> print ("They said, \"What's there?\""), He said, "What's there?", Escape sequences supported by python, Escape Sequence, , DESCRIPTION, , \newline, , Backslash and newline ignored, , \\, , Backslash, , \', , Single quote, , \", , Double quote, , \a, , ASCII Bell, , \b, , ASCII Backspace, , \f, , ASCII Form feed, , \n, , ASCII Linefeed, , \r, , ASCII Carriage Return, , \t, , ASCII Horizontal Tab, , \v, , ASCII Vertical Tab, , \ooo, , Character with octal value ooo, , \xHH, , Character with hexadecimal value HH, , 8.8 The format( ) function, The format( ) function used with strings is very versatile and powerful function used, for formatting strings. The curly braces { } are used as placeholders or replacement fields which, get replaced along with format( ) function., XII Std Computer Science, , Chapter 8.indd 122, , 122, , 20-02-2019 15:20:53
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Example, num1=int (input("Number 1: ")), num2=int (input("Number 2: ")), print ("The sum of { } and { } is { }".format(num1, num2,(num1+num2))), Out Put, Number 1: 34, Number 2: 54, The sum of 34 and 54 is 88, 8.9 Built-in String functions, Python supports the following built-in functions to manipulate string., Syntax, , Description, , len(str), , Returns the length (no of >>> A="Corporation", characters) of the string. >>> print(len(A)), 11, , capitalize( ), , Used to capitalize the first >>> city="chennai", character of the string, >>> print(city.capitalize()), Chennai, , center(width, fillchar), , Returns a string with the >>> str1="Welcome", original string centered to >>> print(str1.center(15,'*') ), a total of width columns, ****Welcome****, and filled with fillchar in, columns that do not have, characters, , find(sub[, start[, end]]), , The function is used to, search the first occurrence, of the sub string in the, given string. It returns, the index at which the, substring starts. It returns, -1 if the substring does, not occur in the string., , 123, , Chapter 8.indd 123, , Example, , >>>str1=’mammals’, >>>str1.find(‘ma’), 0, On omitting the start parameters,, the function starts the search, from the beginning., >>>str1.find(‘ma’,2), 3, >>>str1.find(‘ma’,2,4), -1, Displays -1 because the substring, could not be found between the, index 2 and 4-1., >>>str1.find(‘ma’,2,5), 3, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Syntax, , Description, , Example, , isalnum( ), , Returns True if the string, contains only letters and, digit. It returns False. If, the string contains any, special character like _, @,, #, *, etc., , >>>str1=’Save Earth’, >>>str1.isalnum(), False, The function returns False as space, is an alphanumeric character., >>>’Save1Earth’.isalnum(), True, , isalpha( ), , Returns True if the string >>>’Click123’.isalpha(), contains only letters., False, Otherwise return False. >>>’python’.isalpha( ), True, , isdigit( ), , Returns True if the string >>> str1=’Save Earth’, contains only numbers. >>>print(str1.isdigit( )), Otherwise it returns False., False, , lower( ), , Returns the exact copy >>>str1=’SAVE EARTH’, of the string with all the >>>print(str1.lower()), letters in lowercase., save earth, , islower( ), , Returns True if the string >>> str1=’welcome’, is in lowercase., >>>print (str1.islower( )), True, , isupper( ), , Returns True if the string, is in uppercase., , >>> str1=’welcome’, >>>print (str1.isupper( )), False, , upper( ), , Returns the exact copy of, the string with all letters, in uppercase., , >>> str1=’welcome’, >>>print (str.upper( )), WELCOME, , title( ), , Returns a string in title, case, , >>> str1='education department', >>> print(str1.title()), Education Department, , swapcase( ), , It will change case of, every character to its, opposite case vice-versa., , >>> str1="tAmiL NaDu", >>> print(str1.swapcase()), TaMIl nAdU, , XII Std Computer Science, , Chapter 8.indd 124, , 124, , 20-02-2019 15:20:53
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Syntax, , Description, , Example, , count(str, beg, end), , Returns the number, of substrings occurs, within the given range., Remember that substring, may be a single character., Range (beg and end), arguments are optional., If it is not given, python, searched in whole string., Search is case sensitive., , >>> str1="Raja Raja Chozhan", >>> print(str1.count('Raja')), 2, >>> print(str1.count('r')), 0, >>> print(str1.count('R')), 2, >>> print(str1.count('a')), 5, >>> print(str1.count('a',0,5)), 2, >>> print(str1.count('a',11)), 1, , ord(char ), , Returns the ASCII code, of the character., , >>> ch = 'A', >>> print(ord(ch)), 65, >>> print(ord('B')), 66, , chr(ASII), , Returns the character, represented by a ASCII., , >>> ch=97, >>> print(chr(ch)), a, >>> print(chr(87)), W, , 8.10 Membership Operators, The ‘in’ and ‘not in’ operators can be used with strings to determine whether a string is, present in another string. Therefore, these operators are called as Membership Operators., , Example, str1=input ("Enter a string: "), str2="chennai", if str2 in str1:, print ("Found"), else:, , print ("Not Found"), Output : 1, Enter a string: Chennai G HSS, Saidapet, Found, Output : 2, Enter a string: Govt G HSS, Ashok Nagar, Not Found, 125, , Chapter 8.indd 125, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Example 8.11 Programs using Strings :, Example 8.11.1 : Program to check whether the given string is palindrome, or not, str1 = input ("Enter a string: "), str2 = ' ', index=-1, for i in str1:, str2 += str1[index], index -= 1, print ("The given string = { } \n The Reversed string = { }".format(str1, str2)), if (str1==str2):, print ("Hence, the given string is Palindrome"), else:, print ("Hence, the given is not a palindrome"), Output : 1, Enter a string: malayalam, The given string = malayalam, The Reversed string = malayalam, Hence, the given string is Palindrome, Output : 2, Enter a string: welcome, The given string = welcome, The Reversed string = emoclew, Hence, the given string is not a palindrome, , Example 8.11.2 : Program to display the following pattern, *, * *, * * *, * * * *, * * * * *, str1=' * ', i=1, while i<=5:, print (str1*i), i+=1, Output, *, *, *, *, *, , *, * *, * * *, * * * *, , XII Std Computer Science, , Chapter 8.indd 126, , 126, , 20-02-2019 15:20:53
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Example 8.11.3 : Program to display the number of vowels and consonants, in the given string, str1=input ("Enter a string: "), str2="aAeEiIoOuU", v,c=0,0, for i in str1:, if i in str2:, v+=1, else:, c+=1, print ("The given string contains { } vowels and { } consonants".format(v,c)), Output, Enter a string: Tamilnadu School Education, The given string contains 11 vowels and 15 consonants, , Example 9: Program to create an Abecedarian series. (Abecedarian refers, list of elements appear in alphabetical order), str1="ABCDEFGH", str2="ate", for i in str1:, print ((i+str2),end='\t'), Output, Aate Bate, , Cate Date Eate, , Fate, , Gate Hate, , Example 8.11.4 : Program that accept a string from the user and display, the same after removing vowels from it, def rem_vowels(s):, temp_str='', for i in s:, , if i in "aAeEiIoOuU":, pass, else:, temp_str+=i, print ("The string without vowels: ", temp_str), str1= input ("Enter a String: "), rem_vowels (str1), Output, Enter a String: Mathematical fundations of Computer Science, The string without vowels: Mthmtcl fndtns f Cmptr Scnc, 127, , Chapter 8.indd 127, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Example 8.11.5 : Program that count the occurrences of a character in a, string, def count(s, c):, c1=0, for i in s:, , if i == c:, c1+=1, return c1, str1=input ("Enter a String: "), ch=input ("Enter a character to be searched: "), cnt=count (str1, ch), print ("The given character {} is occurs {} times in the given string".format(ch,cnt)), Out Put, Enter a String: Software Engineering, Enter a character to be searched: e, The given character e is occurs 3 times in the given string, , Points to remember:, • String is a data type in python., • Strings are immutable, that means once you define string, it cannot be changed during, execution., • Defining strings within triple quotes also allows creation of multiline strings., • In a String, python allocate an index value for its each character which is known as, subscript., • The subscript can be positive or negative integer numbers., • Slice is a substring of a main string., • Stride is a third argument in slicing operation., • Escape sequences starts with a backslash and it can be interpreted differently., • The format( ) function used with strings is very versatile and powerful function used, for formatting strings., • The ‘in’ and ‘not in’ operators can be used with strings to determine whether a string, is present in another string., , Hands on Experience, 1. Write a python program to find the length of a string., 2. Write a program to count the occurrences of each word in a given string., XII Std Computer Science, , Chapter 8.indd 128, , 128, , 20-02-2019 15:20:53
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3. Write a program to add a prefix text to all the lines in a string., 4. Write a program to print integers with ‘*’ on the right of specified width., 5. Write a program to create a mirror of the given string. For example, “wel” = “lew“., 6. Write a program to removes all the occurrences of a give character in a string., 7. Write a program to append a string to another string without using += operator., 8. Write a program to swap two strings., 9. Write a program to replace a string with another string without using replace()., 10. Write a program to count the number of characters, words and lines in a given string., , Evaluation, Part - I, , Choose the best answer, , (1 Mark), , 1. Which of the following is the output of the following python code?, str1="TamilNadu", print(str1[::-1]), (a) Tamilnadu, , (b) Tmlau, , (c) udanlimaT, , d) udaNlimaT, , 2. What will be the output of the following code?, str1 = "Chennai Schools", str1[7] = "-", (a) Chennai-Schools, , (b) Chenna-School, , (c) Type error, , (D) Chennai, , 3. Which of the following operator is used for concatenation?, (a) +, , (b) &, , (c) *, , d) =, , 4. Defining strings within triple quotes allows creating:, (a) Single line Strings, , (b) Multiline Strings, , (c) Double line Strings, , (d) Multiple Strings, , 5. Strings in python:, (a) Changeable, , (b) Mutable, , (c) Immutable, , (d) flexible, 129, , Chapter 8.indd 129, , Strings and String Manipulation, , 20-02-2019 15:20:53
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6. Which of the following is the slicing operator?, (a) { }, , (b) [ ], , (c) < >, , (d) ( ), , 7. What is stride?, , 8., , (a) index value of slide operation , , (b) first argument of slice operation, , (c) second argument of slice operation, , (d) third argument of slice operation, , Which of the following formatting character is used to print exponential notation in, upper case?, (a) %e, , 9., , (b) %E, , (c) %g, , (d) %n, , Which of the following is used as placeholders or replacement fields which get replaced, along with format( ) function?, (a) { }, , (b) < >, , (c) ++, , (d) ^^, , 10. The subscript of a string may be:, (a) Positive, , (b) Negative, , (c) Both (a) and (b), , (d) Either (a) or (b), Part -II, , Answer the following questions, , (2 Marks), , 1., , What is String?, , 2., , Do you modify a string in Python?, , 3., , How will you delete a string in Python?, , 4., , What will be the output of the following python code?, str1 = “School”, print(str1*3), , 5., , What is slicing?, , Part -III, , Answer the following questions, 1., , (3 Marks), , Write a Python program to display the given pattern, COMPUTER, COMPUTE, COMPUT, COMPU, COMP, COM, CO, C, , XII Std Computer Science, , Chapter 8.indd 130, , 130, , 20-02-2019 15:20:53
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2., , Write a short about the followings with suitable example:, (a) capitalize( ), , 3., , (b) swapcase( ), , What will be the output of the given python program?, str1 = "welcome", str2 = "to school", str3=str1[:2]+str2[len(str2)-2:], print(str3), , 4., , What is the use of format( )? Give an example., , 5., , Write a note about count( ) function in python., Part -IV, , Answer the following questions, 1., , (5 Marks), , Explain about string operators in python with suitable example., , Reference Books, 1., , https://docs.python.org/3/tutorial/index.html, , 2., , https://www.techbeamers.com/python-tutorial-step-by-step/#tutorial-list, , 3., , Python programming using problem solving approach – Reema Thareja – Oxford University, press., , 4., , Python Crash Course – Eric Matthes – No starch press, San Francisco., , 131, , Chapter 8.indd 131, , Strings and String Manipulation, , 20-02-2019 15:20:53
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Unit III, , CHAPTER 9, LISTS, TUPLES, SETS AND DICTIONARY, , Learning Objectives, After studying this chapter, students will be able to:, • Understand the basic concepts of various collection data types in python such as List,, Tuples, sets and Dictionary., • Work with List, Tuples, sets and Dictionaries using variety of functions., • Writting Python programs using List, Tuples, sets and Dictionaries., • Understand the relationship between List, Tuples and Dictionaries., , 9.1, , Introduction to List, , Python programming language has four collections of data types such as List, Tuples,, Set and Dictionary. A list in Python is known as a “sequence data type” like strings. It is an, ordered collection of values enclosed within square brackets [ ]. Each value of a list is called, as element. It can be of any type such as numbers, characters, strings and even the nested lists, as well. The elements can be modified or mutable which means the elements can be replaced,, added or removed. Every element rests at some position in the list. The position of an element, is indexed with numbers beginning with zero which is used to locate and access a particular, element. Thus, lists are similar to arrays, what you learnt in XI std., , 9.1.1 Create a List in Python, In python, a list is simply created by using square bracket. The elements of list should, be specified within square brackets. The following syntax explains the creation of list., Syntax:, Variable = [element-1, element-2, element-3 …… element-n], , XII Std Computer Science, , Chapter 9.indd 132, , 132, , 20-02-2019 15:21:14
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Example, Marks = [10, 23, 41, 75], Fruits = [“Apple”, “Orange”, “Mango”, “Banana”], MyList = [ ], In the above example, the list Marks has four integer elements; second list Fruits has, four string elements; third is an empty list. The elements of a list need not be homogenous type, of data. The following list contains multiple type elements., Mylist = [ “Welcome”, 3.14, 10, [2, 4, 6] ], In the above example, Mylist contains another list as an element. This type of list is, known as “Nested List”., Nested list is a list containing another list as an element., , 9.1.2 Accessing List elements, Python assigns an automatic index value for each element of a list begins with zero., Index value can be used to access an element in a list. In python, index value is an integer, number which can be positive or negative., , Example, Marks = [10, 23, 41, 75], Marks, 10, Index (Positive) 0, IndexNegative) -4, , 23, 1, -3, , 41, 2, -2, , 75, 3, -1, , Positive value of index counts from the beginning of the list and negative value means, counting backward from end of the list (i.e. in reverse order)., To access an element from a list, write the name of the list, followed by the index of the, element enclosed within square brackets., Syntax:, List_Variable = [E1, E2, E3 …… En], print (List_Variable[index of a element]), , 133, , Chapter 9.indd 133, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:14
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Example (Accessing single element):, >>> Marks = [10, 23, 41, 75], >>> print (Marks[0]), 10, In the above example, print command prints 10 as output, as the index of 10 is zero., , Example: Accessing elements in revevrse order, >>> Marks = [10, 23, 41, 75], >>> print (Marks[-1]), 75, Note, A negative index can be used to access an element in reverse order., , (i) Accessing all elements of a list, Loops are used to access all elements from a list. The initial value of the loop must be, zero. Zero is the beginning index value of a list., , Example, Marks = [10, 23, 41, 75], i=0, while i < 4:, print (Marks[i]), i=i+1, , Output, 10, 23, 41, 75, In the above example, Marks list contains four integer elements i.e., 10, 23, 41, 75. Each, element has an index value from 0. The index value of the elements are 0, 1, 2, 3 respectively., Here, the while loop is used to read all the elements. The initial value of the loop is zero, and, the test condition is i < 4, as long as the test condition is true, the loop executes and prints the, corresponding output., , XII Std Computer Science, , Chapter 9.indd 134, , 134, , 20-02-2019 15:21:14
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During the first iteration, the value of i is zero, where the condition is true. Now, the, following statement print (Marks [i]) gets executed and prints the value of Marks [0] element, ie. 10., The next statement i = i + 1 increments the value of i from 0 to 1. Now, the flow of, control shifts to the while statement for checking the test condition. The process repeats to, print the remaining elements of Marks list until the test condition of while loop becomes false., The following table shows that the execution of loop and the value to be print., Iteration, , i, , while i < 4, , print, (Marks[i]), , 1, , 0, , 0 < 4 True, , Marks [0] = 10, , 0+1=1, , 2, , 1, , 1 < 4 True, , Marks [1] = 23, , 1+1=2, , 3, , 2, , 2 < 4 True, , Marks [2] = 41, , 2+1=3, , 4, , 3, , 3 < 4 True, , Marks [3] = 75, , 3+1=4, , 5, , 4, , 4 < 4 False, , --, , i=i+1, , --, , (ii) Reverse Indexing, Python enables reverse or negative indexing for the list elements. Thus, python lists, index in opposite order. The python sets -1 as the index value for the last element in list and -2, for the preceding element and so on. This is called as Reverse Indexing., , Example, Marks = [10, 23, 41, 75], i = -1, while i >= -4:, print (Marks[i]), i = i + -1, , Output, 75, 41, 23, 10, The following table shows the working process of the above python coding, , 135, , Chapter 9.indd 135, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:14
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Iteration, , i, , while i >= -4, , print ( Marks[i] ), , i = i + -1, , 1, , -1 -1 >= -4 True Marks[-1] = 75, , -1 + (-1) = -2, , 2, , -2 -2 >= -4 True, , Marks[-2] = 41, , -2 + (-1) = -3, , 3, , -3 -3 >= -4 True, , Marks[-3] = 23, , -3 + (-1) = -4, , 4, , -4 -4 >= -4 True, , Marks[-4] = 10, , -4 + (-1) = -5, , 5, , -5 -5 >= -4 False, , --, , --, , 9.1.3 List Length, The len( ) function in Python is used to find the length of a list. (i.e., the number of, elements in a list). Usually, the len( ) function is used to set the upper limit in a loop to read all, the elements of a list. If a list contains another list as an element, len( ) returns that inner list, as a single element., , Example :Accessing single element, >>> MySubject = [“Tamil”, “English”, “Comp. Science”, “Maths”], >>> len(MySubject), 4, , Example : Program to display elements in a list using loop, MySubject = ["Tamil", "English", "Comp. Science", "Maths"], i=0, while i < len(MySubject):, print (MySubject[i]), i=i+1, , Output, Tamil, English, Comp. Science, Maths, , 9.1.4 Accessing elements using for loop, In Python, the for loop is used to access all the elements in a list one by one. This is just, like the for keyword in other programming language such as C++., Syntax:, for index_var in list:, print (index_var), XII Std Computer Science, , Chapter 9.indd 136, , 136, , 20-02-2019 15:21:14
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Here, index_var represents the index value of each element in the list. Python reads, this “for” statement like English: “For (every) element in (the list of) list and print (the name of, the) list items”, , Example, Marks=[23, 45, 67, 78, 98], for x in Marks:, print( x ), , Output, , 23, 45, 67, 78, 98, , In the above example, Marks list has 5 elements; each element is indexed from 0 to 4. The, Python reads the for loop and print statements like English: “For (every) element (represented, as x) in (the list of) Marks and print (the values of the) elements”., , 9.1.5 Changing list elements, In Python, the lists are mutable, which means they can be changed. A list element or, range of elements can be changed or altered by using simple assignment operator (=)., Syntax:, List_Variable [index of an element] = Value to be changed, List_Variable [index from : index to] = Values to changed, Where, index from is the beginning index of the range; index to is the upper limit of, the range which is excluded in the range. For example, if you set the range [0:5] means, Python, takes only 0 to 4 as element index. Thus, if you want to update the range of elements from 1 to, 4, it should be specified as [1:5]., , 137, , Chapter 9.indd 137, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:14
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Example 9.1: Python program to update/change single value, MyList = [2, 4, 5, 8, 10], print ("MyList elements before update... "), for x in MyList:, print (x), MyList[2] = 6, print ("MyList elements after updation... "), for y in MyList:, print (y), , Output:, , MyList elements before update..., 2, 4, 5, 8, 10, MyList elements after updation..., 2, 4, 6, 8, 10, , Example 9.2: Python program to update/change range of values, MyList = [1, 3, 5, 7, 9], print ("List Odd numbers... "), for x in MyList:, print (x), MyList[0:5] = 2,4,6,8,10, print ("List Even numbers... "), for y in MyList:, print (y), , Output, , List Odd numbers..., 1, 3, 5, 7, 9, List Even numbers..., 2, 4, 6, 8, 10, XII Std Computer Science, , Chapter 9.indd 138, , 138, , 20-02-2019 15:21:15
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9.1.6 Adding more elements in a list, , Example, , In Python, append( ) function is, used to add a single element and extend(, ) function is used to add more than one, element to an existing list., , >>> Mylist.extend([71, 32, 29]), >>> print(Mylist), [34, 45, 48, 90, 71, 32, 29], In the above code, extend( ) function, is used to include multiple elements, the, print statement shows all the elements of, the list after the inclusion of additional, elements., , Syntax:, List.append (element to be added), List.extend ( [elements to be added]), In extend( ) function, multiple, elements should be specified within square, bracket as arguments of the function., , 9.1.7 Inserting elements in a list, As you learnt already, append( ), function in Python is used to add more, elements in a list. But, it includes elements, at the end of a list. If you want to include, an element at your desired position, you can, use insert ( ) function. The insert( ) function, is used to insert an element at any position, of a list., , Example, >>> Mylist=[34, 45, 48], >>> Mylist.append(90), >>> print(Mylist), [34, 45, 48, 90], In the above example, Mylist is, created with three elements. Through >>>, Mylist.append(90) statement, an additional, value 90 is included with the existing list, as last element, following print statement, shows all the elements within the list MyList., , Syntax:, List.insert (position index, element), , Example, >>> MyList=[34,98,47,'Kannan', 'Gowrisankar', 'Lenin', 'Sreenivasan' ], >>> print(MyList), [34, 98, 47, 'Kannan', 'Gowrisankar', 'Lenin', 'Sreenivasan'], >>> MyList.insert(3, 'Ramakrishnan'), >>> print(MyList), [34, 98, 47, 'Ramakrishnan', 'Kannan', 'Gowrisankar', 'Lenin', 'Sreenivasan'], In the above example, insert( ) function inserts a new element ‘Ramakrishnan’ at the, index value 3, ie. at the 4th position. While inserting a new element in between the existing, elements, at a particular location, the existing elements shifts one position to the right., 139, , Chapter 9.indd 139, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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9.1.8 Deleting elements from a list, There are two ways to delete an element from a list viz. del statement and remove( ), function. del statement is used to delete known elements whereas remove( ) function is used, to delete elements of a list if its index is unknown. The del statement can also be used to delete, entire list., Syntax:, del List [index of an element], # to delete a particular element, del List [index from : index to], # to delete multiple elements, del List, # to delete entire list, , Example, >>> MySubjects = ['Tamil', 'Hindi', 'Telugu', 'Maths'], >>> print (MySubjects), ['Tamil', 'Hindi', 'Telugu', 'Maths'], >>> del MySubjects[1], >>> print (MySubjects), ['Tamil', 'Telugu', 'Maths'], In the above example, the list MySubjects has been created with four elements. print, statement shows all the elements of the list. In >>> del MySubjects[1] statement, deletes an, element whose index value is 1 and the following print shows the remaining elements of the, list., , Example, >>> del MySubjects[1:3], >>> print(MySubjects), ['Tamil'], In the above codes, >>> del MySubjects[1:3] deletes the second and third elements, from the list. The upper limit of index is specified within square brackets, will be taken as -1 by, the python., , XII Std Computer Science, , Chapter 9.indd 140, , 140, , 20-02-2019 15:21:15
Page 147 : Example, >>> del MySubjects, >>> print(MySubjects), Traceback (most recent call last):, File "<pyshell#9>", line 1, in <module>, print(MySubjects), NameError: name 'MySubjects' is not defined, Here, >>> del MySubjects, deletes the list MySubjects entirely. When you try to print the, elements, Python shows an error as the list is not defined. Which means, the list MySubjects, has been completely deleted., As already stated, the remove( ) function can also be used to delete one or more elements, if the index value is not known. Apart from remove( ) function, pop( ) function can also be, used to delete an element using the given index value. pop( ) function deletes and returns the, last element of a list if the index is not given., The function clear( ) is used to delete all the elements in list, it deletes only the elements, and retains the list. Remember that, the del statement deletes entire list., Syntax:, List.remove(element), # to delete a particular element, List.pop(index of an element), List.clear( ), , Example, >>> MyList=[12,89,34,'Kannan', 'Gowrisankar', 'Lenin'], >>> print(MyList), [12, 89, 34, 'Kannan', 'Gowrisankar', 'Lenin'], >>> MyList.remove(89), >>> print(MyList), [12, 34, 'Kannan', 'Gowrisankar', 'Lenin'], In the above example, MyList has been created with three integer and three string, elements, the following print statement shows all the elements available in the list. In the, statement >>> MyList.remove(89), deletes the element 89 from the list and the print statement, shows the remaining elements., , 141, , Chapter 9.indd 141, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Example, >>> MyList.pop(1), 34, >>> print(MyList), [12, 'Kannan', 'Gowrisankar', 'Lenin'], In the above code, pop( ) function is used to delete a particular element using its index, value, as soon as the element is deleted, the pop( ) function shows the element which is, deleted. pop( ) function is used to delete only one element from a list. Remember that, del, statement deletes multiple elements., , Example, >>> MyList.clear( ), >>> print(MyList), [ ], In the above code, clear( ) function removes only the elements and retains the list. When, you try to print the list which is already cleared, an empty square bracket is displayed without, any elements, which means the list is empty., , 9.1.9 List and range ( ) function, The range( ) is a function used to generate a series of values in Python. Using range( ), function, you can create list with series of values. The range( ) function has three arguments., Syntax of range ( ) function:, range (start value, end value, step value), where,, • start value – beginning value of series. Zero is the default beginning value., • end value – upper limit of series. Python takes the ending value as upper limit – 1., • step value – It is an optional argument, which is used to generate different interval of, values., , XII Std Computer Science, , Chapter 9.indd 142, , 142, , 20-02-2019 15:21:15
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Example : Generating whole numbers upto 10, for x in range (1, 11):, print(x), , Output, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, , Example : Generating first 10 even numbers, for x in range (2, 11, 2):, print(x), , Output, 2, 4, 6, 8, 10, , (i) Creating a list with series of values, Using the range( ) function, you can create a list with series of values. To convert the, result of range( ) function into list, we need one more function called list( ). The list( ), function makes the result of range( ) as a list., Syntax:, List_Varibale = list ( range ( ) ), Note, The list ( ) function is all so used to create list in python., , 143, , Chapter 9.indd 143, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Example, >>> Even_List = list(range(2,11,2)), >>> print(Even_List), [2, 4, 6, 8, 10], In the above code, list( ) function takes the result of range( ) as Even_List elements. Thus,, Even_List list has the elements of first five even numbers., Similarly, we can create any series of values using range( ) function. The following example, explains how to create a list with squares of first 10 natural numbers., , Example : Generating squares of first 10 natural numbers, squares = [ ], for x in range(1,11):, s = x ** 2, squares.append(s), print (squares), In the above program, an empty list is created named “squares”. Then, the for loop, generates natural numbers from 1 to 10 using range( ) function. Inside the loop, the current, value of x is raised to the power 2 and stored in the variables. Each new value of square is, appended to the list “squares”. Finally, the program shows the following values as output., , Output, [1, 4, 9, 16, 25, 36, 49, 64, 81, 100], , 9.1.10 List comprehensions, List comprehension is a simplest way of creating sequence of elements that satisfy a, certain condition., Syntax:, List = [ expression for variable in range ], , Example : Generating squares of first 10 natural numbers using the, concept of List comprehension, >>> squares = [ x ** 2 for x in range(1,11) ], >>> print (squares), , Output:, , [1, 4, 9, 16, 25, 36, 49, 64, 81, 100], , XII Std Computer Science, , Chapter 9.indd 144, , 144, , 20-02-2019 15:21:15
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In the above example, x ** 2 in the expression is evaluated each time it is iterated. This, is the shortcut method of generating series of values., , 9.1.11 Other important list funcion, Function, , copy ( ), , count ( ), , index ( ), , reverse ( ), , sort ( ), , Description, , Syntax, , Example, , Returns a copy of the, list, , List.copy( ), , MyList=[12, 12, 36], x = MyList.copy(), print(x), , Returns the number, of similar elements, present in the last., , List.count(value), , Output:, [12, 12, 36], MyList=[36 ,12 ,12], x = MyList.count(12), print(x), , Returns the index value, of the first recurring, List.index(element), element, , Reverses the order of, the element in the list., , List.reverse( ), , Output:, 2, MyList=[36 ,12 ,12], x = MyList.index(12), print(x), Output:, 0, MyList=[36 ,23 ,12], MyList.reverse(), print(MyList), Output:, [12 ,23 ,36], , Sorts the element in list List.sort(reverse=True|False, key=myFunc), , Both arguments are optional, • If reverse is set as True, list sorting, is in descending order., • Ascending is default., • Key=myFunc; “myFunc” - the name, of the user defined function that, specifies the sorting criteria., , MyList=['Thilothamma', 'Tharani', 'Anitha',, 'SaiSree', 'Lavanya'], MyList.sort( ), print(MyList), MyList.sort(reverse=True), print(MyList), , Output:, ['Anitha', 'Lavanya', 'SaiSree', 'Tharani',, Note: sort( ) will affect the original list. 'Thilothamma'], ['Thilothamma', 'Tharani', 'SaiSree', 'Lavanya',, 'Anitha'], , 145, , Chapter 9.indd 145, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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max( ), , Returns the maximum, value in a list., , max(list), , min( ), , Returns the minimum, value in a list., , min(list), , sum( ), , Returns the sum of, values in a list., , sum(list), , MyList=[21,76,98,23], print(max(MyList)), Output:, 98, MyList=[21,76,98,23], print(min(MyList)), Output:, 21, MyList=[21,76,98,23], print(sum(MyList)), Output:, 218, , 9.1.12 Programs using List, Program 1: write a program that creates a list of numbers from 1 to 20, that are divisible by 4, divBy4=[ ], for i in range(21):, if (i%4==0):, divBy4.append(i), print(divBy4), Output, [0, 4, 8, 12, 16, 20], , Program 2: Write a program to define a list of countries that are a member of, BRICS. Check whether a county is member of BRICS or not, country=["India", "Russia", "Srilanka", "China", "Brazil"], is_member = input("Enter the name of the country: "), if is_member in country:, print(is_member, " is the member of BRICS"), else:, print(is_member, " is not a member of BRICS"), Output, Enter the name of the country: India, India is the member of BRICS, Output, Enter the name of the country: Japan, Japan is not a member of BRICS, XII Std Computer Science, , Chapter 9.indd 146, , 146, , 20-02-2019 15:21:15
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Program 3: Python program to read marks of six subjects and to print the, marks scored in each subject and show the total marks, marks=[], subjects=['Tamil', 'English', 'Physics', 'Chemistry', 'Comp. Science', 'Maths'], for i in range(6):, m=int(input("Enter Mark = ")), marks.append(m), for j in range(len(marks)):, print("{ }. { } Mark = { } ".format(j1+,subjects[j],marks[j])), print("Total Marks = ", sum(marks)), Output, Enter Mark = 45, Enter Mark = 98, Enter Mark = 76, Enter Mark = 28, Enter Mark = 46, Enter Mark = 15, 1. Tamil Mark = 45, 2. English Mark = 98, 3. Physics Mark = 76, 4. Chemistry Mark = 28, 5. Comp. Science Mark = 46, 6. Maths Mark = 15, Total Marks = 308, , Program 4: Python program to read prices of 5 items in a list and then, display sum of all the prices, product of all the prices and find the average, items=[], prod=1, for i in range(5):, print ("Enter price for item { } : ".format(i+1)), p=int(input()), items.append(p), for j in range(len(items)):, print("Price for item { } = Rs. { }".format(j+1,items[j])), prod = prod * items[j], print("Sum of all prices = Rs.", sum(items)), print("Product of all prices = Rs.", prod), print("Average of all prices = Rs.",sum(items)/len(items)), , 147, , Chapter 9.indd 147, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Output:, , Enter price for item 1 :, 5, Enter price for item 2 :, 10, Enter price for item 3 :, 15, Enter price for item 4 :, 20, Enter price for item 5 :, 25, Price for item 1 = Rs. 5, Price for item 2 = Rs. 10, Price for item 3 = Rs. 15, Price for item 4 = Rs. 20, Price for item 5 = Rs. 25, Sum of all prices = Rs. 75, Product of all prices = Rs. 375000, Average of all prices = Rs. 15.0, , Program 5: Python program to count the number of employees earning, more than 1 lakh per annum. The monthly salaries of n number of, employees are given, count=0, n=int(input("Enter no. of employees: ")), print("No. of Employees",n), salary=[], for i in range(n):, print("Enter Monthly Salary of Employee { } Rs.: ".format(i+1)), s=int(input()), salary.append(s), for j in range(len(salary)):, annual_salary = salary[j] * 12, print ("Annual Salary of Employee { } is:Rs. { }".format(j+1,annual_salary)), if annual_salary >= 100000:, , count = count + 1, print("{ } Employees out of { } employees are earning more than Rs. 1 Lakh per annum"., format(count, n)), , XII Std Computer Science, , Chapter 9.indd 148, , 148, , 20-02-2019 15:21:15
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Output:, Enter no. of employees: 5, No. of Employees 5, Enter Monthly Salary of Employee 1 Rs.:, 3000, Enter Monthly Salary of Employee 2 Rs.:, 9500, Enter Monthly Salary of Employee 3 Rs.:, 12500, Enter Monthly Salary of Employee 4 Rs.:, 5750, Enter Monthly Salary of Employee 5 Rs.:, 8000, Annual Salary of Employee 1 is:Rs. 36000, Annual Salary of Employee 2 is:Rs. 114000, Annual Salary of Employee 3 is:Rs. 150000, Annual Salary of Employee 4 is:Rs. 69000, Annual Salary of Employee 5 is:Rs. 96000, 2 Employees out of 5 employees are earning more than Rs. 1 Lakh per annum, , Program 6: Write a program to create a list of numbers in the range 1 to 10., Then delete all the even numbers from the list and print the final list., Num = [], for x in range(1,11):, Num.append(x), print("The list of numbers from 1 to 10 = ", Num), for index, i in enumerate(Num):, if(i%2==0):, del Num[index], print("The list after deleting even numbers = ", Num), Output, The list of numbers from 1 to 10 = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], The list after deleting even numbers = [1, 3, 5, 7, 9], , 149, , Chapter 9.indd 149, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Program 7: Write a program to generate in the Fibonacci series and store it, in a list. Then find the sum of all values., a=-1, b=1, n=int(input("Enter no. of terms: ")), i=0, sum=0, Fibo=[], while i<n:, s=a+b, Fibo.append(s), sum+=s, a=b, b=s, i+=1, print("Fibonacci series upto "+ str(n) +" terms is : " + str(Fibo)), print("The sum of Fibonacci series: ",sum), Output, Enter no. of terms: 10, Fibonacci series upto 10 terms is : [0, 1, 1, 2, 3, 5, 8, 13, 21, 34], The sum of Fibonacci series: 88, , 9.2 Tuples, Introduction to Tuples, Tuples consists of a number of values separated by comma and enclosed within, parentheses. Tuple is similar to list, values in a list can be changed but not in a tuple., The term Tuple is originated from the Latin word represents an abstraction of the, sequence of numbers:, single(1), double(2), triple(3), quadruple(4), quintuple(5), sextuple(6), septuple(7),, octuple(8), ..., n‑tuple, ...,, , 9.2.1 Advantages of Tuples over list, 1. The elements of a list are changeable (mutable) whereas the elements of a tuple are, unchangeable (immutable), this is the key difference between tuples and list., 2. The elements of a list are enclosed within square brackets. But, the elements of a tuple are, enclosed by paranthesis., 3. Iterating tuples is faster than list., XII Std Computer Science, , Chapter 9.indd 150, , 150, , 20-02-2019 15:21:15
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9.2.2 Creating Tuples, Creating tuples is similar to list. In a list, elements are defined within square brackets,, whereas in tuples, they may be enclosed by parenthesis. The elements of a tuple can be even, defined without parenthesis. Whether the elements defined within parenthesis or without, parenthesis, there is no differente in it's function., Syntax:, # Empty tuple, Tuple_Name = ( ), # Tuple with n number elements, Tuple_Name = (E1, E2, E2 ……. En), # Elements of a tuple without parenthesis, Tuple_Name = E1, E2, E3 ….. En, , Example, >>> MyTup1 = (23, 56, 89, 'A', 'E', 'I', "Tamil"), >>> print(MyTup1), , , (23, 56, 89, 'A', 'E', 'I', 'Tamil'), , >>> MyTup2 = 23, 56, 89, 'A', 'E', 'I', "Tamil", >>> print (MyTup2), , , (23, 56, 89, 'A', 'E', 'I', 'Tamil'), , (i) Creating tuples using tuple( ) function, The tuple( ) function is used to create Tuples from a list. When you create a tuple, from a, list, the elements should be enclosed within square brackets., Syntax:, Tuple_Name = tuple( [list elements] ), , Example, >>> MyTup3 = tuple( [23, 45, 90] ), >>> print(MyTup3), , (23, 45, 90), >>> type (MyTup3), <class ‘tuple’>, 151, , Chapter 9.indd 151, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Note, Type ( ) function is used to know the data type of a python object., , (ii) Creating Single element tuple, While creating a tuple with a single element, add a comma at the end of the element., In the absence of a comma, Python will consider the element as an ordinary data type; not a, tuple. Creating a Tuple with one element is called “Singleton” tuple., , Example, >>> MyTup4 = (10), >>> type(MyTup4), <class 'int'>, >>> MyTup5 = (10,), >>> type(MyTup5), <class 'tuple'>, , 9.2.3 Accessing values in a Tuple, Like list, each element of tuple has an index number starting from zero. The elements of, a tuple can be easily accessed by using index number., , Example, >>> Tup1 = (12, 78, 91, “Tamil”, “Telugu”, 3.14, 69.48), # to access all the elements of a tuple, >>> print(Tup1), , (12, 78, 91, 'Tamil', 'Telugu', 3.14, 69.48), #accessing selected elements using indices, >>> print(Tup1[2:5]), , (91, 'Tamil', 'Telugu'), #accessing from the first element up to the specified index value, >>> print(Tup1[:5]), , (12, 78, 91, 'Tamil', 'Telugu'), # accessing from the specified element up to the last element., >>> print(Tup1[4:]), , ('Telugu', 3.14, 69.48), # accessing from the first element to the last element, >>> print(Tup1[:]), , (12, 78, 91, 'Tamil', 'Telugu', 3.14, 69.48), XII Std Computer Science, , Chapter 9.indd 152, , 152, , 20-02-2019 15:21:15
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9.2.4 Update and Delete Tuple, As you know a tuple is immutable, the elements in a tuple cannot be changed. Instead of, altering values in a tuple, joining two tuples or deleting the entire tuple is possible., , Example, # Program to join two tuples, Tup1 = (2,4,6,8,10), Tup2 = (1,3,5,7,9), Tup3 = Tup1 + Tup2, print(Tup3), , Output, (2, 4, 6, 8, 10, 1, 3, 5, 7, 9), To delete an entire tuple, the del command can be used., Syntax:, del tuple_name, , Example, Tup1 = (2,4,6,8,10), print("The elements of Tup1 is ", Tup1), del Tup1, print (Tup1), Output:, The elements of Tup1 is (2, 4, 6, 8, 10), Traceback (most recent call last):, File "D:/Python/Tuple Examp 1.py", line 4, in <module>, print (Tup1), NameError: name 'Tup1' is not defined, Note that, the print statement in the above code prints the elements. Then, the del statement, deletes the entire tuple. When you try to print the deleted tuple, Python shows the error., , 9.2.5 Tuple Assignment, Tuple assignment is a powerful feature in Python. It allows a tuple variable on the left, of the assignment operator to be assigned to the values on the right side of the assignment, 153, , Chapter 9.indd 153, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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operator. Each value is assigned to its respective variable., a, , b, , c, , =, , 34, , 90, , 76, , Example, >>> (a, b, c) = (34, 90, 76), >>> print(a,b,c), 34 90 76, # expression are evaluated before assignment, >>> (x, y, z, p) = (2**2, 5/3+4, 15%2, 34>65), >>> print(x,y,z,p), 4 5.666666666666667 1 False, Note that, when you assign values to a tuple, ensure that the number of values on both sides of, the assignment operator are same; otherwise, an error is generated by Python., , 9.2.6 Returning multiple values in Tuples, A function can return only one value at a time, but Python returns more than one value, from a function. Python groups multiple values and returns them together., , Example : Program to return the maximum as well as minimum values in, a list, def Min_Max(n):, a = max(n), b = min(n), return(a, b), Num = (12, 65, 84, 1, 18, 85, 99), (Max_Num, Min_Num) = Min_Max(Num), print("Maximum value = ", Max_Num), print("Minimum value = ", Min_Num), Output:, Maximum value = 99, Minimum value = 1, , XII Std Computer Science, , Chapter 9.indd 154, , 154, , 20-02-2019 15:21:15
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9.2.7 Nested Tuples, In Python, a tuple can be defined inside another tuple; called Nested tuple. In a nested, tuple, each tuple is considered as an element. The for loop will be useful to access all the, elements in a nested tuple., , Example, Toppers = (("Vinodini", "XII-F", 98.7), ("Soundarya", "XII-H", 97.5),, , ("Tharani", "XII-F", 95.3), ("Saisri", "XII-G", 93.8)), for i in Toppers:, print(i), Output:, ('Vinodini', 'XII-F', 98.7), ('Soundarya', 'XII-H', 97.5), ('Tharani', 'XII-F', 95.3), ('Saisri', 'XII-G', 93.8), Note, All the functions used in List can be applicable even for tuples., , 9.2.8 Programs using Tuples, Program 1: Write a program to swap two values using tuple assignment, a = int(input("Enter value of A: ")), b = int(input("Enter value of B: ")), print("Value of A = ", a, "\n Value of B = ", b), (a, b) = (b, a), print("Value of A = ", a, "\n Value of B = ", b), , Output:, Enter value of A: 54, Enter value of B: 38, Value of A = 54, Value of B = 38, Value of A = 38, Value of B = 54, , 155, , Chapter 9.indd 155, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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Program 2: Write a program using a function that returns the area and, circumference of a circle whose radius is passed as an argument.two values, using tuple assignment, pi = 3.14, def Circle(r):, return (pi*r*r, 2*pi*r), radius = float(input("Enter the Radius: ")), (area, circum) = Circle(radius), print ("Area of the circle = ", area), print ("Circumference of the circle = ", circum), , Output:, , Enter the Radius: 5, Area of the circle = 78.5, Circumference of the circle = 31.400000000000002, , Program 3: Write a program that has a list of positive and negative numbers., Create a new tuple that has only positive numbers from the list, Numbers = (5, -8, 6, 8, -4, 3, 1), Positive = ( ), for i in Numbers:, if i > 0:, , , Positive += (i, ), , print("Positive Numbers: ", Positive), Output:, Positive Numbers: (5, 6, 8, 3, 1), , 9.3, , Sets, , Introduction, In python, a set is another type of collection data type. A Set is a mutable and an unordered, collection of elements without duplicates. That means the elements within a set cannot be, repeated. This feature used to include membership testing and eliminating duplicate elements., , XII Std Computer Science, , Chapter 9.indd 156, , 156, , 20-02-2019 15:21:15
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9.3.1 Creating a Set, A set is created by placing all the elements separated by comma within a pair of curly, brackets. The set( ) function can also used to create sets in Python., Syntax:, Set_Variable = {E1, E2, E3 …….. En}, , Example, >>> S1={1,2,3,'A',3.14}, >>> print(S1), {1, 2, 3, 3.14, 'A'}, >>> S2={1,2,2,'A',3.14}, >>> print(S2), {1, 2, 'A', 3.14}, In the above examples, the set S1 is created with different types of elements without, duplicate values. Whereas in the set S2 is created with duplicate values, but python accepts, only one element among the duplications. Which means python removed the duplicate value,, because a set in python cannot have duplicate elements., Note, When you print the elements from a set, python shows the values in different order., , 9.3.2 Creating Set using List or Tuple, A list or Tuple can be converted as set by using set( ) function. This is very simple, procedure. First you have to create a list or Tuple then, substitute its variable within set( ), function as argument., , Example, MyList=[2,4,6,8,10], MySet=set(MyList), print(MySet), Output:, {2, 4, 6, 8, 10}, , 157, , Chapter 9.indd 157, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:15
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9.3.3 Set Operations, As you learnt in mathematics, the python is also supports the set operations such as, Union, Intersection, difference and Symmetric difference., , (i) Union: It includes all elements from two or more sets, , Set A, , Set B, , In python, the operator | is used to union of two sets. The function union( ) is also used, to join two sets in python., , Example: Program to Join (Union) two sets using union operator, set_A={2,4,6,8}, set_B={'A', 'B', 'C', 'D'}, U_set=set_A|set_B, print(U_set), , Output:, {2, 4, 6, 8, 'A', 'D', 'C', 'B'}, , Example: Program to Join (Union) two sets using union function, set_A={2,4,6,8}, set_B={'A', 'B', 'C', 'D'}, set_U=set_A.union(set_B), print(set_U), , Output:, , {'D', 2, 4, 6, 8, 'B', 'C', 'A'}, , XII Std Computer Science, , Chapter 9.indd 158, , 158, , 20-02-2019 15:21:15
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(ii) Intersection: It includes the common elements in two sets, , Set A, , Set B, , The operator & is used to intersect two sets in python. The function intersection( ) is, also used to intersect two sets in python., , Example: Program to insect two sets using intersection operator, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A & set_B), , Output:, {'A', 'D'}, , Example: Program to insect two sets using intersection function, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A.intersection(set_B)), , Output:, {'A', 'D'}, , 159, , Chapter 9.indd 159, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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(iii) Difference, It includes all elements that are in first set (say set A) but not in the second set (say set B), , Set A, , Set B, , The minus (-) operator is used to difference set operation in python. The function, difference( ) is also used to difference operation., , Example: Program to difference of two sets using minus operator, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A - set_B), , Output:, {2, 4}, , Example: Program to difference of two sets using difference function, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A.difference(set_B)), , Output:, {2, 4}, , XII Std Computer Science, , Chapter 9.indd 160, , 160, , 20-02-2019 15:21:16
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(iv) Symmetric difference, It includes all the elements that are in two sets (say sets A and B) but not the one that are, common to two sets., , Set A, , Set B, , The caret (^) operator is used to symmetric difference set operation in python. The, function symmetric_difference( ) is also used to do the same operation., , Example: Program to symmetric difference of two sets using caret operator, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A ^ set_B), , Output:, {2, 4, 'B', 'C'}, , Example: Program to difference of two sets using symmetric difference, function, set_A={'A', 2, 4, 'D'}, set_B={'A', 'B', 'C', 'D'}, print(set_A.symmetric_difference(set_B)), , Output:, {2, 4, 'B', 'C'}, , 161, , Chapter 9.indd 161, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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9.3.4 Programs using Sets, Program 1: Program that generate a set of prime numbers and another set of even, numbers. Demonstrate the result of union, intersection, difference and symmetirc, difference operations., , Example, even=set([x*2 for x in range(1,11)]), primes=set(), for i in range(2,20):, j=2, f=0, while j<i/2:, if i%j==0:, f=1, j+=1, if f==0:, primes.add(i), print("Even Numbers: ", even), print("Prime Numbers: ", primes), print("Union: ", even.union(primes)), print("Intersection: ", even.intersection(primes)), print("Difference: ", even.difference(primes)), print("Symmetric Difference: ", even.symmetric_difference(primes)), Output:, Even Numbers: {2, 4, 6, 8, 10, 12, 14, 16, 18, 20}, Prime Numbers: {2, 3, 4, 5, 7, 11, 13, 17, 19}, Union: {2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20}, Intersection: {2, 4}, Difference: {6, 8, 10, 12, 14, 16, 18, 20}, Symmetric Difference: {3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20}, , 9.4, , Dictionaries, , Introduction, In python, a dictionary is a mixed collection of elements. Unlike other collection data, types such as a list or tuple, the dictionary type stores a key along with its element. The keys in, a Python dictionary is separated by a colon ( : ) while the commas work as a separator for the, elements. The key value pairs are enclosed with curly braces { }., , XII Std Computer Science, , Chapter 9.indd 162, , 162, , 20-02-2019 15:21:16
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Syntax of defining a dictionary:, Dictionary_Name = {, , Key_1: Value_1,, , , , Key_2:Value_2,, , , , …….., , , , Key_n:Value_n, , , , }, , Key in the dictionary must be unique case sensitive and can be of any valid Python type., , 9.4.1 Creating a Dictionary, # Empty dictionary, Dict1 = { }, # Dictionary with Key, Dict_Stud = { RollNo: 1234, Name:Murali, Class:XII, Marks:451}, , 9.4.2 Dictionary Comprehensions, In Python, comprehension is another way of creating dictionary. The following is the, syntax of creating such dictionary., Syntax, Dict = { expression for variable in sequence [if condition] }, , The if condition is optional and if specified, only those values in the sequence are evaluated, using the expression which satisfy the condition., , Example, Dict = { x : 2 * x for x in range(1,10)}, Output of the above code is, {1: 2, 2: 4, 3: 6, 4: 8, 5: 10, 6: 12, 7: 14, 8: 16, 9: 18}, , 9.4.3 Accessing, Adding, Modifying and Deleting elements from a Dictionary, Accessing all elements from a dictionary is very similar as Lists and Tuples. Simple print, function is used to access all the elements. If you want to access a particular element, square, brackets can be used along with key., , 163, , Chapter 9.indd 163, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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Example : Program to access all the values stored in a dictionary, MyDict = {, 'Reg_No': '1221',, 'Name' : 'Tamilselvi',, 'School' : 'CGHSS',, 'Address' : 'Rotler St., Chennai 112' }, print(MyDict), print("Register Number: ", MyDict['Reg_No']), print("Name of the Student: ", MyDict['Name']), print("School: ", MyDict['School']), print("Address: ", MyDict['Address']), , Output:, , {'Reg_No': '1221', 'Name': 'Tamilselvi', 'School': 'CGHSS', 'Address': 'Rotler St., Chennai 112'}, , Register Number: 1221, Name of the Student: Tamilselvi, School: CGHSS, Address: Rotler St., Chennai 112, , Note that, the first print statement prints all the values of the dictionary. Other statements, are printing only the specified values which is given within square brackets., In an existing dictionary, you can add more values by simply assigning the value along, with key. The following syntax is used to understand adding more elements in a dictionary., dictionary_name [key] = value/element, , Example : Program to add a new value in the dictionary, MyDict = {, 'Reg_No': '1221',, 'Name' : 'Tamilselvi',, 'School' : 'CGHSS', 'Address' : ', , Rotler St., Chennai 112'}, print(MyDict), print("Register Number: ", MyDict['Reg_No']), print("Name of the Student: ", MyDict['Name']), MyDict['Class'] = 'XII - A' , # Adding new value, print("Class: ", MyDict['Class']) , # Printing newly added value, print("School: ", MyDict['School']), print("Address: ", MyDict['Address']), Modification of a value in dictionary is very similar as adding elements. When you assign, a value to a key, it will simply overwrite the old value., In Python dictionary, del keyword is used to delete a particular element. The clear( ), function is used to delete all the elements in a dictionary. To remove the dictionary, you can, use del keyword with dictionary name., XII Std Computer Science, , Chapter 9.indd 164, , 164, , 20-02-2019 15:21:16
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Syntax:, # To delete a particular element., del dictionary_name[key], # To delete all the elements, dictionary_name.clear( ), # To delete an entire dictionary, del dictionary_name, , Example : Program to delete elements from a dictionary and finally deletes, the dictionary., Dict = {'Roll No' : 12001, 'SName' : 'Meena', 'Mark1' : 98, 'Marl2' : 86}, print("Dictionary elements before deletion: \n", Dict), del Dict['Mark1'] , # Deleting a particular element, print("Dictionary elements after deletion of a element: \n", Dict), Dict.clear() , # Deleting all elements, print("Dictionary after deletion of all elements: \n", Dict), del Dict, print(Dict) # Deleting entire dictionary, Output:, Dictionary elements before deletion:, , {'Roll No': 12001, 'SName': 'Meena', 'Mark1': 98, 'Marl2': 86}, Dictionary elements after deletion of a element:, , {'Roll No': 12001, 'SName': 'Meena', 'Marl2': 86}, Dictionary after deletion of all elements:, { }, Traceback (most recent call last):, , File "E:/Python/Dict_Test_02.py", line 8, in <module>, print(Dict), NameError: name 'Dict' is not defined, , 9.4.4 Difference between List and Dictionary, (1) List is an ordered set of elements. But, a dictionary is a data structure that is used for, matching one element (Key) with another (Value)., (2) The index values can be used to access a particular element. But, in dictionary key, represents index. Remember that, key may be a number of a string., (3) Lists are used to look up a value whereas a dictionary is used to take one value and look, up another value., 165, , Chapter 9.indd 165, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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Points to remember:, • Python programming language has four collections of data types such as List, Tuple,, Set and Dictionary., • A list is known as a “sequence data type”. Each value of a list is called as element., • The elements of list should be specified within square brackets., • Each element has a unique value called index number begins with zero., • Python allows positive and negative values as index., • Loops are used access all elements from a list., • The “for” loop is a suitable loop to access all the elements one by one., • The append ( ), extend ( ) and insert ( ) functions are used to include more elements, in a List., • The del, remove ( ) and pop ( ) are used to delete elements from a list., • The range ( ) function is used to generate a series of values., • Tuples consists of a number of values separated by comma and enclosed within, parentheses., • Iterating tuples is faster than list., • The tuple ( ) function is also used to create Tuples from a list., • Creating a Tuple with one element is called “Singleton” tuple., • A Set is a mutable and an unordered collection of elements without duplicates., • A set is created by placing all the elements separated by comma within a pair of curly, brackets., • A dictionary is a mixed collection of elements., , Hands on Experience, 1. Write a program to remove duplicates from a list., 2. Write a program that prints the maximum value in a Tuple., 3. Write a program that finds the sum of all the numbers in a Tuples using while loop., 4. Write a program that finds sum of all even numbers in a list., , XII Std Computer Science, , Chapter 9.indd 166, , 166, , 20-02-2019 15:21:16
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5. Write a program that reverse a list using a loop., 6. Write a program to insert a value in a list at the specified location., 7. Write a program that creates a list of numbers from 1 to 50 that are either divisible by 3 or, divisible by 6., 8. Write a program to create a list of numbers in the range 1 to 20. Then delete all the numbers, from the list that are divisible by 3., 9. Write a program that counts the number of times a value appears in the list. Use a loop to, do the same., 10. Write a program that prints the maximum and minimum value in a dictionary., , Evaluation, Part - I, , Choose the best answer, , (1 Marks), , 1. Pick odd one in connection with collection data type, (a) List, , (b) Tuple, , (c) Dictionary, , (d) Loop, , 2. Let list1=[2,4,6,8,10], then print(List1[-2]) will result in, (a) 10, , (b) 8, , (c) 4, , (d) 6, , 3. Which of the following function is used to count the number of elements in a list?, (a) count() (b) find(), , (c)len(), , (d) index(), , 4. If List=[10,20,30,40,50] then List[2]=35 will result, (a) [35,10,20,30,40,50], , (b) [10,20,30,40,50,35], , (c) [10,20,35,40,50], , (d) [10,35,30,40,50], , 5. If List=[17,23,41,10] then List.append(32) will result, , 6., , (a) [32,17,23,41,10] , , (b) [17,23,41,10,32], , (c) [10,17,23,32,41] , , (d) [41,32,23,17,10], , Which of the following Python function can be used to add more than one element, within an existing list?, (a) append(), , (b) append_more(), , (c)extend(), , (d) more(), , 7. What will be the result of the following Python code?, S=[x**2 for x in range(5)], 167, , Chapter 9.indd 167, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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print(S), (a) [0,1,2,4,5] (b) [0,1,4,9,16], , (c) [0,1,4,9,16,25], , (d) [1,4,9,16,25], , 8. What is the use of type() function in python?, (a) To create a Tuple, (b) To know the type of an element in tuple., (c) To know the data type of python object., (d) To create a list., 9. Which of the following statement is not correct?, (a) A list is mutable, (b) A tuple is immutable., (c) The append() function is used to add an element., (d) The extend() function is used in tuple to add elements in a list., 10. Let setA={3,6,9}, setB={1,3,9}. What will be the result of the following snippet?, print(setA|setB), (a) {3,6,9,1,3,9}, , (b) {3,9} , , (c) {1} , , (d) {1,3,6,9}, , 11. Which of the following set operation includes all the elements that are in two sets but not, the one that are common to two sets?, , 12., , (a) Symmetric difference , , (b) Difference, , (c) Intersection , , (d) Union, , The keys in Python, dictionary is specified by, (a) =, , (b) ;, , (c)+, , (d) :, , Part - II, , Answer the following questions, , (2 Marks), , 1. What is List in Python?, 2. How will you access the list elements in reverse order?, 3. What will be the value of x in following python code?, List1=[2,4,6[1,3,5]], x=len(List1), 4. Differentiate del with remove( ) function of List., XII Std Computer Science, , Chapter 9.indd 168, , 168, , 20-02-2019 15:21:16
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5. Write the syntax of creating a Tuple with n number of elements., 6. What is set in Python?, Part - III, , Answer the following questions, , (3 Marks), , 1. What are the advantages of Tuples over a list?, 2. Write a shot note about sort( )., 3. What will be the output of the following code?, list = [2**x for x in range(5)], print(list), 4. Explain the difference between del and clear( ) in dictionary with an example., 5. List out the set operations supported by python., 6. What are the difference between List and Dictionary?, Part - IV, , Answer the following questions, , (5 Marks), , 1. What the different ways to insert an element in a list. Explain with suitable example., 2. What is the purpose of range( )? Explain with an example., 3. What is nested tuple? Explain with an example., 4. Explain the different set operations supported by python with suitable example., , References, 1. https://docs.python.org/3/tutorial/index.html, 2. https://www.techbeamers.com/python-tutorial-step-by-step/#tutorial-list, 3. Python programming using problem solving approach – Reema Thareja – Oxford, University press., 4. Python Crash Course – Eric Matthes – No starch press, San Francisco., , 169, , Chapter 9.indd 169, , Lists, Tuples, Sets and Dictionary, , 20-02-2019 15:21:16
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Unit, , III, , CHAPTER 10, PYTHON CLASSES AND OBJECTS, , Learning Objectives, After the completion of this chapter, the student is able to, • Understand the fundamental concepts of Object Oriented Programming like: Classes,, Objects, Constructor and Destructor., • Gain the knowledge of creating classes and objects in Python., • Create classes with Constructors., • Write complex programs in Python using classes., , 10.1 Introduction, Python is an Object Oriented Programming language. Classes and Objects are the key, features of Object Oriented Programming. Theoretical concepts of classes and objects are very, similar to that of C++. But, creation and implementation of classes and objects is very simple, in Python compared to C++., Class is the main building block in Python. Object is a collection of data and function, that act on those data. Class is a template for the object. According to the concept of Object, Oriented Programming, objects are also called as instances of a class or class variable. In, Python, everything is an object. For example, all integer variables that we use in our program, is an object of class int. Similarly all string variables are also object of class string., , 10.2 Defining classes, In Python, a class is defined by using the keyword class. Every class has a unique name, followed by a colon ( : )., Syntax:, class class_name:, statement_1, statement_2, ………….., ………….., statement_n, , XII Std Computer Science, , Chapter 10.indd 170, , 170, , 20-02-2019 15:21:36
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Where, statement in a class definition may be a variable declaration, decision control,, loop or even a function definition. Variables defined inside a class are called as “Class Variable”, and functions are called as “Methods”. Class variable and methods are together known as, members of the class. The class members should be accessed through objects or instance of, class. A class can be defined anywhere in a Python program., , Example: Program to define a class, class Sample:, , , x, y = 10, 20 , , # class variables, , In the above code, name of the class is Sample and it has two variables x and y having, the initial value 10 and 20 respectively. To access the values defined inside the class, you need, an object or instance of the class., , 10.3 Creating Objects, Once a class is created, next you should create an object or instance, of that class. The process of creating object is called as “Class Instantiation”., Syntax:, Object_name = class_name( ), Note that the class instantiation uses function notation ie. class_name with, , 10.4 Accessing Class Members, Any class member ie. class variable or method (function) can be accessed by using, object with a dot ( . ) operator., Syntax:, Object_name . class_member, , Example : Program to define a class and access its member variables, class Sample:, #class variables, x, y = 10, 20, S=Sample( ) , # class instantiation, print("Value of x = ", S.x), print("Value of y = ", S.y), print("Value of x and y = ", S.x+S.y), Output :, Value of x = 10, Value of y = 20, Value of x and y = 30, 171, , Chapter 10.indd 171, , Python Classes and Objects, , 20-02-2019 15:21:36
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In the above code, the name of the class is Sample. Inside the class, we have assigned, the variables x and y with initial value 10 and 20 respectively. These two variables are called as, class variables or member variables of the class. In class instantiation process, we have created, an object S to access the members of the class. The first two print statements simply print the, value of class variable x and y and the last print statement add the two values and print the, result., , 10.5 Class Methods, Python class function or Method is very similar to ordinary function with a small, difference that, the class method must have the first argument named as self. No need to pass, a value for this argument when we call the method. Python provides its value automatically., Even if a method takes no arguments, it should be defined with the first argument called self., If a method is defined to accept only one argument it will take it as two arguments ie. self and, the defined argument., When you declare class variable within class, methods must be prefixed by the class, name and dot operator., Note, The statements defined inside the class must be properly indented., , Example 10.2: Program to find total and average marks using class, class Student:, mark1, mark2, mark3 = 45, 91, 71 , , #class variable, , def process(self): #class method, sum = Student.mark1 + Student.mark2 + Student.mark3, avg = sum/3, print("Total Marks = ", sum), print("Average Marks = ", avg), return, S=Student(), S.process(), In the above program, after defining the class, an object S is created. The statement, S.process( ), calls the function to get the required output., , XII Std Computer Science, , Chapter 10.indd 172, , 172, , 20-02-2019 15:21:36
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Note that, we have declared three variables mark1, mark2 and mark3 with the values, 45, 91, 71 respectively. We have defined a method named process with self argument, which, means, we are not going to pass any value to that method. First, the process method adds the, values of the class variables, stores the result in the variable sum, finds the average and displays, the result., Thus the above code will show the following output., , Output, Total Marks = 207, Average Marks = 69.0, , Example : program to check and print if the given number is odd or, even using class, class Odd_Even:, even = 0 , #class varaiable, def check(self, num):, if num%2==0:, , print(num," is Even number"), else:, , print(num," is Odd number"), n=Odd_Even(), x = int(input("Enter a value: ")), n.check(x), When you execute this program, Python accepts the value entered by the user, and passes it to the method check through object., Output 1, Enter a value: 4, 4 is Even number, Output 2, Enter a value: 5, 5 is Odd number, , 10.6 Constructor and Destructor in Python, Constructor is the special function that is automatically executed when an object of a, class is created. In Python, there is a special function called “init” which act as a Constructor., It must begin and end with double underscore. This function will act as an ordinary function;, but only difference is, it is executed automatically when the object is created. This constructor, function can be defined with or without arguments. This method is used to initialize the class, variables., 173, , Chapter 10.indd 173, , Python Classes and Objects, , 20-02-2019 15:21:36
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General format of __init__ method (Constructor function), def __init__(self, [args ……..]):, <statements>, , Example : Program to illustrate Constructor, class Sample:, def __init__(self, num):, , print("Constructor of class Sample..."), self.num=num, , print("The value is :", num), S=Sample(10), The above class “Sample”, has only a constructor with one argument named as num., When the constructor gets executed, first the print statement, prints the “Constructor of class, Sample….”, then, the passing value to the constructor is assigned to self.num and finally it, prints the value passed along with the given string., The above constructor gets executed automatically, when an object S is created with, actual parameter 10. Thus, the Python display the following output., , , Constructor of class Sample..., , , , The value is : 10, , Class variable defined within constructor keep count of number of objects created with, the class., , Example : Program to illustrate class variable to keep count of number, of objects created., class Sample:, num=0, def __init__(self, var):, Sample.num+=1, self.var=var, , print("The object value is = ", var), , print("The count of object created = ", Sample.num), S1=Sample(15), S2=Sample(35), S3=Sample(45), , XII Std Computer Science, , Chapter 10.indd 174, , 174, , 20-02-2019 15:21:36
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In the above program, class variable num is shared by all three objects of the class, Sample. It is initialized to zero and each time an object is created, the num is incremented by, 1. Since, the variable shared by all objects, change made to num by one object is reflected in, other objects as well. Thus the above program produces the output given below., Output, The object value is, , =, , 15, , The count of object created, , =, , 1, , The object value is, , =, , 35, , The count of object created, , =, , 2, , The object value is, , =, , 45, , The count of object created, , =, , 3, , Note: class variable is similar to static type in C++, Destructor is also a special method gets executed automatically when an object exit, from the scope. It is just opposite to constructor. In Python, __del__( ) method is used as, destructor., , Example : Program to illustrate about the __del__( ) method, class Sample:, num=0, def __init__(self, var):, Sample.num+=1, self.var=var, , print("The object value is = ", var), , print("The value of class variable is= ", Sample.num), def __del__(self):, Sample.num-=1, , print("Object with value %d is exit from the scope"%self.var), S1=Sample(15), S2=Sample(35), S3=Sample(45), , 10.7 Public and Private Data Members, The variables which are defined inside the class is public by default. These variables can, be accessed anywhere in the program using dot operator., A variable prefixed with double underscore becomes private in nature. These variables, can be accessed only within the class., , 175, , Chapter 10.indd 175, , Python Classes and Objects, , 20-02-2019 15:21:36
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Example : Program to illustrate private and public variables, class Sample:, def __init__(self, n1, n2):, self.n1=n1, self.__n2=n2, def display(self):, , print("Class variable 1 = ", self.n1), , print("Class variable 2 = ", self.__n2), S=Sample(12, 14), S.display(), print("Value 1 = ", S.n1), print("Value 2 = ", S.__n2), In the above program, there are two class variables n1 and n2 are declared. The variable, n1 is a public variable and n2 is a private variable. The display( ) member method is defined to, show the values passed to these two variables., The print statements defined within class will successfully display the values of n1 and, n2, even though the class variable n2 is private. Because, in this case, n2 is called by a method, defined inside the class. But, when we try to access the value of n2 from outside the class, Python throws an error. Because, private variable cannot be accessed from outside the class., , Output, Class variable 1 = 12, Class variable 2 = 14, Value 1 = 12, Traceback (most recent call last):, , , File "D:/Python/Class-Test-04.py", line 12, in <module>, , , , print("Value 2 = ", S.__n2), , AttributeError: 'Sample' object has no attribute '__n2', , XII Std Computer Science, , Chapter 10.indd 176, , 176, , 20-02-2019 15:21:36
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10.8 Sample Programs to illustrate classes and objects, Program 1: Write a program to calculate area and circumference of a circle, class Circle:, pi=3.14, def __init__(self,radius):, self.radius=radius, def area(self):, return Circle.pi*(self.radius**2), def circumference(self):, return 2*Circle.pi*self.radius, r=int(input("Enter Radius: ")), C=Circle(r), print("The Area =",C.area()), print("The Circumference =", C.circumference()), Output:, Enter Radius: 5, The Area = 78.5, The Circumference = 31.400000000000002, Program 2: write a menu driven program that keeps record of books, available in you school library, class Library:, def __init__(self):, self.bookname="", self.author="", def getdata(self):, self.bookname = input("Enter Name of the Book: "), self.author = input("Enter Author of the Book: "), def display(self):, print("Name of the Book: ",self.bookname), print("Author of the Book: ",self.author), print(“\n”), , 177, , Chapter 10.indd 177, , Python Classes and Objects, , 20-02-2019 15:21:36
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book=[] #empty list, ch = 'y', while(ch=='y'):, print("1. Add New Book \n 2.Display Books"), resp = int(input("Enter your choice : ")), if(resp==1):, L=Library(), L.getdata(), book.append(L), elif(resp==2):, for x in book:, x.display(), else:, print("Invalid input...."), ch = input("Do you want continue...."), Output:, 1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: Programming in C++, Enter Author of the Book: K. Kannan, Do you want continue....y, 1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: Learn Python, Enter Author of the Book: V.G.Ramakrishnan, Do you want continue....y, , XII Std Computer Science, , Chapter 10.indd 178, , 178, , 20-02-2019 15:21:36
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1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: Advanced Python, Enter Author of the Book: Dr. Vidhya, Do you want continue....y, 1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: Working with OpenOffice, Enter Author of the Book: N.V.Gowrisankar, Do you want continue....y, 1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: Data Structure, Enter Author of the Book: K.Lenin, Do you want continue....y, 1. Add New Book, 2.Display Books, Enter your choice : 1, Enter Name of the Book: An Introduction to Database System, Enter Author of the Book: R.Sreenivasan, Do you want continue....y, 1. Add New Book, 2.Display Books, , 179, , Chapter 10.indd 179, , Python Classes and Objects, , 20-02-2019 15:21:36
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Enter your choice : 2, Name of the Book: Programming in C++, Author of the Book: K. Kannan, Name of the Book: Learn Python, Author of the Book: V.G.Ramakrishnan, Name of the Book: Advanced Python, Author of the Book: Dr. Vidhya, Name of the Book: Working with OpenOffice, Author of the Book: N.V.Gowrisankar, Name of the Book: Data Structure, Author of the Book: K.Lenin, Name of the Book: An Introduction to Database System, Author of the Book: R.Sreenivasan, Do you want continue....n, Program 3: Write a program to accept a string and print the number of, uppercase, lowercase, vowels, consonants and spaces in the given string, class String:, def __init__(self):, self.uppercase=0, self.lowercase=0, self.vowels=0, self.consonants=0, self.spaces=0, self.string="", def getstr(self):, self.string=str(input("Enter a String: ")), , XII Std Computer Science, , Chapter 10.indd 180, , 180, , 20-02-2019 15:21:36
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def count_upper(self):, for ch in self.string:, if (ch.isupper()):, self.uppercase+=1, def count_lower(self):, for ch in self.string:, if (ch.islower()):, self.lowercase+=1, def count_vowels(self):, for ch in self.string:, , if (ch in ('A', 'a', 'e', 'E', 'i', 'I', 'o', 'O', 'l', 'L')):, self.vowels+=1, def count_consonants(self):, for ch in self.string:, , if (ch not in ('A', 'a', 'e', 'E', 'i', 'I', 'o', 'O', 'l', 'L')):, self.consonants+=1, def count_space(self):, for ch in self.string:, , if (ch==" "):, self.spaces+=1, def execute(self):, self.count_upper(), self.count_lower(), self.count_vowels(), self.count_consonants(), self.count_space(), def display(self):, print("The given string contains..."), print("%d Uppercase letters"%self.uppercase), print("%d Lowercase letters"%self.lowercase), print("%d Vowels"%self.vowels), print("%d Consonants"%self.consonants), print("%d Spaces"%self.spaces), , 181, , Chapter 10.indd 181, , Python Classes and Objects, , 20-02-2019 15:21:36
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S = String(), S.getstr(), S.execute(), S.display(), Output, Enter a String: Welcome To Learn Computer Science, The given string contains..., 5 Uppercase letters, 24 Lowercase letters, 13 Vowels, 20 Consonants, 4 Spaces, Program 4: Write a program to store product and its cost price. Display all the, available products and prompt to enter quantity of all the products. Finally, generate a bill which displays the total amount to be paid, class MyStore:, __prod_code=[], __prod_name=[], __cost_price=[], __prod_quant=[], def getdata(self):, self.p = int(input("Enter no. of products you need to store: ")), for x in range(self.p):, , , self.__prod_code.append(int(input("Enter Product Code: "))), , , , self.__prod_name.append(str(input("Enter Product Name: "))), , , , self.__cost_price.append(int(input("Enter Cost price: "))), , XII Std Computer Science, , Chapter 10.indd 182, , 182, , 20-02-2019 15:21:36
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def display(self):, print("Stock in Stores"), print("----------------------------------------------------------"), print("Product Code \t Product Name \t Cost Price"), print("----------------------------------------------------------"), for x in range(self.p):, , print(self.__prod_code[x], "\t\t", self.__prod_name[x], "\t\t", self.__cost_, price[x]), print("----------------------------------------------------------"), def print_bill(self):, total_price = 0, for x in range(self.p):, , , q=int(input("Enter the quantify for the product code %d : "%self.__, , prod_code[x])), self.__prod_quant.append(q), total_price = total_price +self.__cost_price[x]*self.__prod_quant[x], print(" Invoice Receipt "), print("-----------------------------------------------------------------------------"), print("Product Code\t Product Name\t Cost Price\t Quantity \t Total Amount"), print("-----------------------------------------------------------------------------"), for x in range(self.p):, , print(self.__prod_code[x], "\t\t", self.__prod_name[x], "\t\t",, , self.__cost_price[x], "\t\t", self.__prod_quant[x], "\t\t",, self.__prod_quant[x]*self.__cost_price[x]), print("-----------------------------------------------------------------------------"), print(" Total Amount = ", total_price), , 183, , Chapter 10.indd 183, , Python Classes and Objects, , 20-02-2019 15:21:36
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S=MyStore(), S.getdata(), S.display(), S.print_bill(), Output:, Enter no. of products you need to store: 5, Enter Product Code: 101, Enter Product Name: Product-A, Enter Cost price: 25, Enter Product Code: 201, Enter Product Name: Product-B, Enter Cost price: 35, Enter Product Code: 301, Enter Product Name: Product-C, Enter Cost price: 35, Enter Product Code: 401, Enter Product Name: Product-D, Enter Cost price: 50, Enter Product Code: 501, Enter Product Name: Product-E, Enter Cost price: 120, Stock in Stores, -------------------------------------------------------------------------------------Product Code , Product Name, Cost Price, -------------------------------------------------------------------------------------101 Product-A 25, 201 Product-B 35, 301 Product-C 35, 401 Product-D 50, 501 Product-E 120, --------------------------------------------------------------------------------------, , XII Std Computer Science, , Chapter 10.indd 184, , 184, , 20-02-2019 15:21:36
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Enter the quantify for the product code 101 : 10, Enter the quantify for the product code 201 : 15, Enter the quantify for the product code 301 : 10, Enter the quantify for the product code 401 : 20, Enter the quantify for the product code 501 : 10, Invoice Receipt, --------------------------------------------------------------------------------------------------Product Code, Product Name, Cost Price Quantity Total Amount, --------------------------------------------------------------------------------------------------101 , Product-A , 25 , 10 , 250, 201 , Product-B , 35 , 15 , 525, 301 , Product-C , 35 , 10 , 350, 401 , Product-D , 50 , 20 , 1000, 501 , Product-E , 120 , 10 , 1200, --------------------------------------------------------------------------------------------- , Total Amount = 3325, ----------------------------------------------------------------------------------------------, , Points to remember, • Python is an Object Oriented Programming language., • Classes and Objects are the key features of Object Oriented Programming., • In Python, a class is defined by using the keyword class., • Variables defined inside a class is called as “Class Variable” and function are, called as “Methods”., • The process of creating object is called as “Class Instantiation”., • Constructor is the special function that is automatically executed when an, object of a class is created., • In Python, there is a special function called “init” is used as Constructor., • Destructor is also a special method gets execution automatically when an, object exits from the scope., • In Python, __del__( ) method is used as destructor., • A variable prefixed with double underscore is becomes private in nature., , 185, , Chapter 10.indd 185, , Python Classes and Objects, , 20-02-2019 15:21:36
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Hands on Experience, 1. Write a program using class to store name and marks of students in list and print total, marks., 2. Write a program using class to accept three sides of a triangle and print its area., 3. Write a menu driven program to read, display, add and subtract two distances., , Evaluation, Part - I, , Choose the best answer, 1., , 2., , 3., , 4., , 5., , 6., , Which of the following are the key features of an Object Oriented Programming language?, (a) Constructor and Classes, , (b) Constructor and Object, , (c) Classes and Objects, , (d) Constructor and Destructor, , Functions defined inside a class:, (a) Functions, , (b) Module, , (c) Methods, , (d) section, , Class members are accessed through which operator?, (a) &, , (b) ., , (c) #, , (d) %, , Which of the following method is automatically executed when an object is created?, (a) __object__( ), , (b) __del__( ), , (c) __func__( ), , (d) __init__( ), , A private class variable is prefixed with, (a) __, , (b) &&, , (c) ##, , (d) **, , Which of the following method is used as destructor?, (a) __init__( ), , (b) __dest__( ), , (c) __rem__( ), , (d) __del__( ), , XII Std Computer Science, , Chapter 10.indd 186, , (1 Marks), , 186, , 20-02-2019 15:21:36
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7., , 8., , Which of the following class declaration is correct?, (a) class class_name, , (b) class class_name<>, , (c) class class_name:, , (d) class class_name[ ], , Which of the following is the output of the following program?, , class Student:, , , def __init__(self, name):, , self.name=name, S=Student(“Tamil”), , 9., , (a) Error, , (b) Tamil, , (c) name, , (d) self, , Which of the following is the private class variable?, (a) __num, , (b) ##num, , (c) $$num, , (d) &&num, , 10. The process of creating an object is called as:, (a) Constructor, , (b) Destructor, , (c) Initialize, , (d) Instantiation, Part -II, , Answer the following questions, , (2 Marks), , 1., , What is class?, , 2., , What is instantiation?, , 3., , What is the output of the following program?, , class Sample:, , , __num=10, , , , def disp(self):, , print(self.__num), S=Sample(), S.disp(), print(S.__num), 4., , How will you create constructor in Python?, , 5., , What is the purpose of Destructor?, , 187, , Chapter 10.indd 187, , Python Classes and Objects, , 20-02-2019 15:21:37
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Part -III, , Answer the following questions, , (3 Marks), , 1. What are class members? How do you define it?, 2. Write a class with two private class variables and print the sum using a method., 3. Find the error in the following program to get the given output?, class Fruits:, , def __init__(self, f1, f2):, self.f1=f1, self.f2=f2, , def display(self):, , print("Fruit 1 = %s, Fruit 2 = %s" %(self.f1, self.f2)), F = Fruits ('Apple', 'Mango'), del F.display, F.display(), Output, , , Fruit 1 = Apple, Fruit 2 = Mango, , 4. What is the output of the following program?, class Greeting:, def __init__(self, name):, , self.__name = name, def display(self):, , print("Good Morning ", self.__name), obj=Greeting('Bindu Madhavan'), obj.display(), 5. How do define constructor and destructor in Python?, Part -IV, , Answer the following questions, 1., , (5 Marks), , Write a menu driven program to add or delete stationary items. You should use dictionary, to store items and the brand., , References, 1., , https://docs.python.org/3/tutorial/index.html, , 2., , https://www.techbeamers.com/python-tutorial-step-by-step/#tutorial-list, , 3., , Python programming using problem solving approach – Reema Thareja – Oxford University, press., , 4., , Python Crash Course – Eric Matthes – No starch press, San Francisco., , XII Std Computer Science, , Chapter 10.indd 188, , 188, , 20-02-2019 15:21:37
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Unit IV, , CHAPTER 11, DATABASE CONCEPTS, Example : 600006, DPI Campus, SCERT,, Chennai, College Road, , Learning Objectives, , 11.2 Information, , At the completion of this chapter, the student, will be able to know, , Information is formatted data, which, allows to be utilized in a significant way., Example, SCERT, College Road, DPI Campus, Chennai 600006, As you can see, from the example above, data appears as a set, of words and numbers. However, when the, data is processed, organized and formatted,, it gives a meaningful information about the, SCERT institution contact address., , • the concept of a database and relational, database., • different components of the database., • types of database models., • types of relationship., • the concepts of relational algebra., , Introduction, A database is an organized collection, of data, generally stored and accessed, electronically from a computer system. The, term "database" is also used to refer to any, of the DBMS, the database system or an, application associated with the database., Because of the close relationship between, them, the term "database" is often used, casually to refer to both a database and, the DBMS used to manipulate it. A school, class register is a database where names are, arranged alphabetically. Databases have, been around since people started recording, things. Here we tend to focus on electronic, ones., , 11.3 Database, Database is a repository collection of, related data organized in a way that data can, be easily accessed, managed and updated., Database can be a software or hardware, based, with one sole purpose of storing data., , 11.4 DataBase Management, System (DBMS), A DBMS is a software that allows us, to create, define and manipulate database,, allowing users to store, process and analyze, data easily. DBMS provides us with an, interface or a tool, to perform various, operations to create a database, storing of, data and for updating data, etc. DBMS also, provides protection and security to the, , 11.1 Data, Data are raw facts stored in a, computer. A data may contain any character,, text, word or a number., 189, , Chapter 11.indd 189, , 20-02-2019 15:22:46
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databases. It also maintains data consistency in case of multiple users., Examples of DBMS softwares are : Foxpro, dbase., , 11.4.1 Characteristics of Database Management System, 1. Data stored into Tables Data is never directly stored into the database. Data is stored, into tables, created inside the database. DBMS also allows to, have relationship between tables which makes the data more, meaningful and connected., 2. Reduced Redundancy, , In the modern world hard drives are very cheap, but earlier, when hard drives were too expensive, unnecessary repetition, of data in database was a big problem But DBMS follows, Normalisation which divides the data in such a way that, repetition is minimum., , 3.Data Consistency, , On live data, it is being continuously updated and added,, maintaining the consistency of data can become a challenge., But DBMS handles it by itself., , 4. Support Multiple user DBMS allows multiple users to work on it(update, insert,, and Concurrent Access delete data) at the same time and still manages to maintain the, data consistency., 5.Query Language, , DBMS provides users with a simple query language, using, which data can be easily fetched, inserted, deleted and updated, in a database., , 6. Security, , The DBMS also takes care of the security of data, protecting, the data from unauthorized access. In a typical DBMS, we can, create user accounts with different access permissions, using, which we can easily secure our data by restricting user access., , 7. DBMS Supports, Transactions, , It allows us to better handle and manage data integrity in real, world applications where multi-threading is extensively used., , 11.4.2 Advantages of DBMS, • Segregation of application program, • Minimal data duplication or Data Redundancy, • Easy retrieval of data using the Query Language, • Reduced development time and maintenance, , XII Std Computer Science, , Chapter 11.indd 190, , 190, , 20-02-2019 15:22:47
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11.4.3 Components of DBMS, , 3. Data: It is that resource for which DBMS, is designed. DBMS creation is to store and, utilize data., , The Database Management System, can be divided into five major components, as follows:, , 4. Procedures/Methods: They are general, instructions to use a database management, system such as installation of DBMS,, manage databases to take backups, report, generation, etc., , 1.Hardware , 2.Software 3.Data, 4.Procedures/Methods, 5.Database Access Languages, , 5. DataBase Access Languages: They are, the languages used to write commands to, access, insert, update and delete data stored, in any database., , Hardware, , Examples of popular DBMS: Dbase,, FoxPro, , 11.5 Database Structure, , Software, , DATA, , Data Base, Access, Languages, , Table is the entire collection of, related data in one table, referred to as a File, or Table where the data is organized as row, and column., , Procedures, / Methods, , USER, Components of DBMS, , Each row in a table represents a, record, which is a set of data for each, database entry., , Figure 11.1, , Each table column represents a Field,, which groups each piece or item of data, among the records into specific categories or, types of data. Eg. StuNo., StuName, StuAge,, StuClass, StuSec., , 1. Hardware: The computer, hard disk, I/O, channels for data, and any other physical, component involved in storage of data, 2. Software: This main component is, a program that controls everything. The, DBMS software is capable of understanding, the Database Access Languages and, interprets into database, commands for, execution., , A Table is known as a RELATION, A Row is known as a TUPLE, A column is known as an ATTRIBUTE, , 191, , Chapter 11.indd 191, , Database Concepts, , 20-02-2019 15:22:47
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Tuple / Row, , Attribute / Column, StuNo, 1101, 1102, 1103, 1104, 1105, , StuName, StuAge, Kannan, 14, Ramakrishnan, 14, Vidhya, 14, Britto, 15, Padmaja, 14, , StuClass StuSec, 9, A, 9, A, 10, B, 9, A, 10, B, , Table / Relation, DataBase Structure, Fig 11.2, , 11.6 Data Model, • A data model describes how the data can be represented and accessed from a software after, complete implementation, • It is a simple abstraction of complex real world data gathering environment., • The main purpose of data model is to give an idea as how the final system or software will, look like after development is completed., 11.6.1 Types of Data Model, Following are the different types of a Data Model, • Hierarchical Model, • Relational Model, • Network Database Model, • Entity Relationship Model, • Object Model, 1. Hierarchical Model, Hierarchical model was developed by IBM as Information Management System., In Hierarchical model, data is represented as a simple tree like structure form. This, model represents a one-to-many relationship ie parent-child relationship. One child can have, only one parent but one parent can have many children. This model is mainly used in IBM, Main Frame computers., , XII Std Computer Science, , Chapter 11.indd 192, , 192, , 20-02-2019 15:22:47
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School, , Course, , Resources, , Lab, , Theory, , Hierarchical Model Fig. 11.3, , 2. Relational Model, The Relational Database model was first proposed by E.F. Codd in 1970 . Nowadays, it, is the most widespread data model used for database applications around the world., The basic structure of data in relational model is tables (relations). All the information’s, related to a particular type is stored in rows of that table. Hence tables are also known as, relations in a relational model. A relation key is an attribute which uniquely identifies a, particular tuple (row in a relation (table))., Stu_id, 1, 2, 3, , Name, Malar, Suncar, Velu, , Age, 17, 16, 16, , Subj_id, 1, 2, 3, , Stu_id, 1, 1, 3, , Subj_id, 1, 2, 2, , Name, C++, Php, Python, , Teacher, Kannan, Ramakrishnan, Vidhya, , Marks, 92, 89, 96, , Relational Model, Fig. 11.4, , 3. Network Model, Network database model is an extended form of hierarchical data model. The difference, between hierarchical and Network data model is :, • In hierarchical model, a child record has only one parent node,, , 193, , Chapter 11.indd 193, , Database Concepts, , 20-02-2019 15:22:47
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• In a Network model, a child may have many parent nodes. It represents the data in manyto-many relationships., • This model is easier and faster to access the data., School, , Library, , Staff Room This child has one parent node, , Office, , Student, , Student has 3 parent node, , Network Model, Fig. 11.5, School represents the parent node, Library, Office and Staff room is a child to school (parent node), Student is a child to library, office and staff room (one to many relationship), 4. Entity Relationship Model. (ER model), In this database model, relationship are created by dividing the object into entity and its, characteristics into attributes., It was developed by Chen in 1976. This model is useful in developing a conceptual, design for the database. It is very simple and easy to design logical view of data. The developer, can easily understand the system by looking at ER model constructed., Rectangle represents the entities. E.g. Doctor and Patient, Ellipse represents the attributes E.g. D-id, D-name, P-id, P-name. Attributes describes, the characteristics and each entity becomes a major part of the data stored in the database., Diamond represents the relationship in ER diagrams, E.g. Doctor diagnosis the Patient, , XII Std Computer Science, , Chapter 11.indd 194, , 194, , 20-02-2019 15:22:47
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Doctor, D-id, , Diagnosis, , Patient, P-id, , D-Name, , P-Name, , ER model, Fig. 11.6, 5. Object Model, Object model stores the data in the form of objects, attributes and methods, classes and, Inheritance. This model handles more complex applications, such as Geographic information, System (GIS), scientific experiments, engineering design and manufacturing. It is used in file, Management System. It represents real world objects, attributes and behaviors. It provides a, clear modular structure. It is easy to maintain and modify the existing code., Shape, get_area(), get_perimeter(), , Circle, Radius, , Rectangle, Length, breath, , Triangle, Base, Height, , Object Model, Fig. 11.7, An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects, in this model., • Circle has the attribute radius., •, , Rectangle has the attributes length and breadth., , • Triangle has the attributes base and height ., • The objects Circle, Rectangle and Triangle inherit from the object Shape., 11.6.2 Types of DBMS Users, Database Administrators, Database Administrator or DBA is the one who manages the complete database, management system. DBA takes care of the security of the DBMS, managing the license keys,, managing user accounts and access etc., , 195, , Chapter 11.indd 195, , Database Concepts, , 20-02-2019 15:22:47
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Application Programmers or Software Developers, This user group is involved in developing and designing the parts of DBMS., End User, All modern applications, web or mobile, store user data. Applications are programmed, in such a way that they collect user data and store the data on DBMS systems running on their, server. End users are the one who store, retrieve, update and delete data., Database designers: are responsible for identifying the data to be stored in the database for, choosing appropriate structures to represent and store the data., , 11.7 Difference between DBMS and RDBMS, Basis of Comparison, , DBMS, , RDBMS, , Expansion, , Database Management System, , Relational DataBase, Management System, , Data storage, , Navigational model, ie data by linked records, , Relational model (in tables)., ie data in tables as row and, column, , Data redundancy, , Exhibit, , Not Present, , Normalization, , Not performed, , RDBMS uses normalization, to reduce redundancy, , Data access, , Consumes more time, , Faster, compared to DBMS., , Keys and indexes, , Does not use., , used to establish, relationship. Keys are used in, RDBMS., , Transaction, management, , Inefficient,, Error prone and insecure., , Efficient and secure., , Distributed Databases, , Not supported, , Supported by RDBMS., , Example, , Dbase, FoxPro., , SQL server, Oracle, mysql,, MariaDB, SQLite., , Database normalization was first proposed by Dr. Edgar F Codd as an integral part, of RDBMS in order to reduce data redundancy and improve data integrity. These rules are, known as E F Codd Rules., , XII Std Computer Science, , Chapter 11.indd 196, , 196, , 20-02-2019 15:22:47
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staff, , 11.8 Types of Relationships, , members., Staff, , Following are the types of relationships used, in a database., , Department, Gajalakshmi, , 1. One-to-One Relationship, 2. One-to-Many Relationship, , Computer, , 3. Many-to-One Relationship, 4. Many-to-Many Relationship, 1. One-to-One Relationship, In One-to-One Relationship, one, entity is related with only one other entity., One row in a table is linked with only one, row in another table and vice versa., , Jayapandiyan, Sarojini, , Radha, , Maths, , Ramesh, , One to Many Mapping, Fig 11.9, , Exam No, , Tamilselvi, , Tamil, , Malaiarasu, , For example: A student can have only, one exam number, Student, , Bindhu, , 3. Many-to-One Relationship, , 1001, , In Many-to-One Relationship, many, entities can be related with only one in the, other entity., , 1002, , For example: A number of staff, members working in one Department., Multiple rows in staff members table, is related with only one row in Department, table., , 1003, , Staff, One to one Relationships, Fig 11.8, , Suganya, , 2. One-to-Many Relationship, , Bala, , In One-to-Many relationship, one, entity is related to many other entities., , Valarmathi, , One row in a table A is linked to, many rows in a table B, but one row in a, table B is linked to only one row in table A., For example: One Department has many, , Computer, Maths, , Many to one Relationship, Fig 11.10, 197, , Chapter 11.indd 197, , Department, , Database Concepts, , 20-02-2019 15:22:47
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4. Many-to-Many Relationship, , 11.9 Relational Algebra in DBMS, , A, many-to-many, relationship, occurs when multiple records in a table are, associated with multiple records in another, table., , What is Relational Algebra?, Relational Algebra, was first created, by Edgar F Codd while at IBM. It was used, for modeling the data stored in relational, databases and defining queries on it., , Example 1: Customers and Product, Customers can purchase various, products and Products can be purchased by, many customers, , Relational Algebra is a procedural, query language used to query the database, tables using SQL., , Example 2: Students and Courses, , Relational algebra operations are, performed recursively on a relation (table), to yield an output. The output of these, operations is a new relation, which might be, formed by one or more input relations., , A student can register for many, Courses and a Course may include many, stu d e nt s, Example 3: Books and Student., to, , Many Books in a Library are issued, many students., Book, , Relational Algebra is divided into various, groups, , Student, , Unary Relational Operations, SELECT ( symbol : σ), , C++, , Kalaivani, , SQL, , Manjula, , Relational Algebra Operations from Set, Theor y, , Sridevi, , • UNION (∪), , python, , PROJECT ( symbol : ∏), , • INTERSECTION (∩), • DIFFERENCE (−), , Many to Many Relationship, Fig 11.11, , • CARTESIAN PRODUCT, SELECT (symbol : σ), , The relational model, was invented by Edgar, Frank Codd (Father of, Relational DataBase) as, a general model of data, and, subsequently promoted by Chris Date, and Hugh Darwen among others., , XII Std Computer Science, , Chapter 11.indd 198, , (X), , General form σ ( R ) with a relation, c, R and a condition C on the attributes of R., The SELECT operation is used for, selecting a subset with tuples according to a, given condition., Select filters out all tuples that do not, satisfy C., 198, , 20-02-2019 15:22:47
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STUDENT, Studno, , Name, , Course, , Year, , cs1, , Kannan, , Big Data, , II, , cs2, , Gowri Shankar, , R language, , I, , cs3, , Lenin, , Big Data, , I, , cs4, , Padmaja, , Python Programming, , I, , Table 11.1, , σcourse = “Big Data” (STUDENT ), Studno, , Name, , Course, , Year, , cs1, , Kannan, , Big Data, , II, , cs3, , Lenin, , Big Data, , I, , PROJECT (symbol : Π), The projection eliminates all attributes of the input relation but those mentioned in, the projection list. The projection method defines a relation that contains a vertical subset of, Relation., Example 1 using Table 11.1, Πcourse (STUDENT), Result, Course, Big Data, R language, Python Programming, Note, duplicate row is removed in the result, , 199, , Chapter 11.indd 199, , Database Concepts, , 20-02-2019 15:22:47
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Example 2 (using Table 11.1), Πstudno, course (STUDENT), Result, Studno, , Course, , cs1, , Big Data, , cs2, , R language, , cs3, , Big Data, , cs4, , Python Programming, , UNION (Symbol :∪), It includes all tuples that are in tables A or in B. It also eliminates duplicates. Set A, Union Set B would be expressed as A ∪ B, Example 3, Consider the following tables, Table A, , Table B, , Studno, , Name, , Studno, , Name, , cs1, , Kannan, , cs1, , Kannan, , cs3, , Lenin, , cs2, , GowriShankarn, , cs4, , Padmaja, , cs3, , Lenin, , Table 11.2, Result, Table A ∪ B, , Studno, , Name, , cs1, , Kannan, , cs2, , GowriShankar, , cs3, , Lenin, , cs4, , Padmaja, , SET DIFFERENCE ( Symbol : - ), The result of A – B, is a relation which includes all tuples that are in A but not in B., The attribute name of A has to match with the attribute name in B., Example 4 ( using Table 11.2), XII Std Computer Science, , Chapter 11.indd 200, , 200, , 20-02-2019 15:22:47
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Result, Table A - B, , cs4, , Padmaja, , INTERSECTION (symbol : ∩) A ∩ B, Defines a relation consisting of a set of all tuple that are in both in A and B. However, A, and B must be union-compatible., Example 5 (using Table 11.2), A∩B, , cs1, , Kannan, , cs3, , Lenin, , PRODUCT OR CARTESIAN PRODUCT (Symbol : X ), Cross product is a way of combining two relations. The resulting relation contains, both, relations being combined., A x B means A times B, where the relation A and B have different attributes., This type of operation is helpful to merge columns from two relations., Table A, , Table B, , Table A x Table B, , 1, , S, , 2, 3, , R, , 1 S, 1 R, 2 S, 2 R, , Table A = 3, Table B = 2, Table A x B = 3 x 2 = 6, , 3 S, 3 R, , Cartesian Product, Fig. 11.12, Table A, , Table B, , studno, , name, , studno, , subject, , cs1, , Kannan, , cs28, , Big Data, , cs2, , Gowri Shankar, , cs62, , R language, , cs4, , Padmaja, , cs25, , python programming, , Table 11.3, 201, , Chapter 11.indd 201, , Database Concepts, , 20-02-2019 15:22:48
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Cartesian product : Table A x Table B, studno, , name, , course, , subject, , cs1, , Kannan, , cs28, , Big Data, , cs1, , Kannan, , cs62, , R language, , cs1, , Kannan, , cs25, , python rogramming, , cs2, , Gowri Shankar, , cs28, , Big Data, , cs2, , Gowri Shankar, , cs62, , R language, , cs2, , Gowri Shankar, , cs25, , python programming, , cs4, , Padmaja, , cs28, , Big Data, , cs4, , Padmaja, , cs62, , R language, , cs4, , Padmaja, , cs25, , python programming, , Points to remember:, • DBMS is a computer based record keeping system, • Data is unprocessed data which contains any character, text, word or number, has no meaning, • Information is processed data, organized and formatted., • Examples of RDBMS are mysql, oracle, sql server, ibm db2, • Redundancy means duplication of data in a database., • Data Consistency means that data values are the same at all instances of a, database, • Data Integrity is security from unauthorized users, • Table is known a relation, • A row is called a tuple, • A column is known as an attribute, • Types of data model are Hierarchical, Relational, Network, ER and Object, model., • Hierarchical model is a simple tree like structure form with one-to-one, relationship called parent-child relationship, • Relational Model represents data as relations or tables, • Network model is similar to Hierarchical model but it allows a record to have, more than one parent, • ER model consists of entities, attributes and relationships, , XII Std Computer Science, , Chapter 11.indd 202, , 202, , 20-02-2019 15:22:48
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Points to remember:, • Object model stores data as objects, attributes, methods, classes and inheritance, • Normalization reduces data redundancy and improves data integrity, • Different types of Relationship are one-to-one, one-to-many, many-to-one and, many-to-many relationships, • Database Normalization was proposed by Dr.Edgar F Codd, • Relational Algebra is used for modeling data stored in relational databases and, for defining queries on it., , Evaluation, Part - A, , Choose the best answer, , (1 Marks), , 1. What is the acronym of DBMS?, , 2, , 3, , 4, , 5, , a) DataBase Management Symbol, , b) Database Managing System, , c) DataBase Management System, , d) DataBasic Management System, , A table is known as, a) tuple, , b) attribute, , c) relation, , d)entity, , Which database model represents parent-child relationship?, a) Relational, , b) Network, , c) Hierarchical, , d) Object, , Relational database model was first proposed by, a) E F Codd, , b) E E Codd, , c) E F Cadd, , d) E F Codder, , What type of relationship does hierarchical model represents?, a) one-to-one, , b) one-to-many, , c) many-to-one, , d) many-to-many, , 6. Who is called Father of Relational Database from the following?, a) Chris Date, , b)Hugh Darween, , c) Edgar Frank Codd, , d) Edgar Frank Cadd, 203, , Chapter 11.indd 203, , Database Concepts, , 20-02-2019 15:22:48
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7. Which of the following is an RDBMS?, , 8, , a) Dbase, , b) Foxpro, , c) Microsoft Access, , d) SQLite, , What symbol is used for SELECT statement?, a) σ , , 9, , b) Π, , d) Ω, , c) X, , A tuple is also known as, a) table, , b) row, , c) attribute, , d) field, , 10. Who developed ER model?, a) Chen, , b) EF Codd, , c) Chend, , d) Chand, Part - B, , Answer the following questions, , (2 Marks), , 1., , Mention few examples of a database., , 2., , List some examples of RDBMS., , 3., , What is data consistency?, , 4., , What is the difference between Hierarchical and Network data model?, , 5., , What is normalization?, Part -C, , Answer the following questions, , (3 Marks), , 1., , What is the difference between Select and Project command?, , 2., , What is the role of DBA?, , 3., , Explain Cartesian Product with a suitable example., , 4., , Explain Object Model with example., , 5., , Write a note on different types of DBMS users., Part -D, , Answer the following questions, , (5 Marks), , 1., , Explain the different types of data model., , 2., , Explain the different types of relationship mapping., , 3., , Differentiate DBMS and RDBMS., , 4., , Explain the different operators in Relational algebra with suitable examples., , 5., , Explain the characteristics of DBMS., , XII Std Computer Science, , Chapter 11.indd 204, , 204, , 20-02-2019 15:22:48
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Unit, , IV, , CHAPTER 12, STRUCTURED QUERY LANGUAGE, , Learning Objectives, After studying this lesson, students will be able to:, • The processing skills of SQL., • The components of SQL., • To create a table by specifying the fields and records., • To apply various manipulations like inserting, updating and deleting records in a table., • To learn about various constraints and to apply it on tables., • To generate queries in the table by applying various clauses., • To modify the structure of an existing table., • The commands to delete records, table and revoke the commands., , 12.1 Introduction to SQL, The Structured Query Language (SQL) is a standard programming language to access, and manipulate databases. SQL allows the user to create, retrieve, alter, and transfer information, among databases. It is a language designed for managing and accessing data in a Relational, Data Base Management System (RDBMS)., There are many versions of SQL. The original version was developed at IBM’s Research, centre and originally called as Sequel in early 1970’s. Later the language was changed to SQL., In 1986, ANSI (American National Standard Institute) published an SQL standard that was, updated again in 1992, the latest SQL was released in 2008 and named as SQL 2008., Note, Latest SQL standard as of now is SQL 2008, released in 2008., , 12.2 Role of SQL in RDBMS, RDBMS stands for Relational DataBase Management System. Oracle, MySQL, MS SQL, Server, IBM DB2 and Microsoft Access are RDBMS packages. SQL is a language used to access, data in such databases., 205, , Chapter 12.indd 205, , 20-02-2019 15:30:40
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In general, Database is a collection of tables that store sets of data that can be queried, for use in other applications. A database management system supports the development,, administration and use of database platforms. RDBMS is a type of DBMS with a row-based, table structure that connects related data elements and includes functions related to Create,, Read, Update and Delete operations, collectively known as CRUD., The data in RDBMS, is stored in database objects, called Tables. A table is a collection, of related data entries and it consist of rows and columns., A field is a column in a table that is designed to maintain specific related information, about every record in the table. It is a vertical entity that contains all information associated, with a specific field in a table. The fields in a student table may be of the type AdmnNo,, StudName, StudAge, StudClass, Place etc., A Record is a row, which is a collection of related fields or columns that exist in a table., A record is a horizontal entity in a table which represents the details of a particular student in, a student table., , 12.3 Processing Skills of SQL, The various processing skills of SQL are :, 1., , Data Definition Language (DDL) : The SQL DDL provides commands for defining, relation schemas (structure), deleting relations, creating indexes and modifying relation, schemas., , 2., , Data Manipulation Language (DML) : The SQL DML includes commands to insert,, delete, and modify tuples in the database., , 3., , Embedded Data Manipulation Language : The embedded form of SQL is used in high, level programming languages., , 4., , View Definition : The SQL also includes commands for defining views of tables., , 5., , Authorization : The SQL includes commands for access rights to relations and views of, tables., , 6., , Integrity : The SQL provides forms for integrity checking using condition., , 7., , Transaction control : The SQL includes commands for file transactions and control over, transaction processing., SQL-Structured Query Language is a language used for accessing databases while, MySQL is a database management system, like SQL Server, Oracle, Informix,, Postgres, etc. MySQL is a RDBMS., Refer installing MYSQL in Annexure -1, , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 206, , 206, , 20-02-2019 15:30:40
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12.4 Creating Database, 1., , To create a database, type the following command in the prompt:, CREATE DATABASE database_name;, For example to create a database to store the tables:, CREATE DATABASE stud;, , 2., , To work with the database, type the following command., USE DATABASE;, For example to use the stud database created, give the command, USE stud;, WAMP stands for “Windows, Apache, MySQL and PHP”. WAMP is a variation of, LAMP for windows systems and is installed as a software bundle (Apache, MySQL, and PHP). It is often used for web development and internal testing, but may also be used, to serve live websites., , 12.5 Components of SQL, SQL commands are divided into five categories:, DML - Data Manipulation Language, DDL - Data Definition Language, DCL - Data Control Language, TCL - Transaction Control Language, DQL - Data Query Language, 12.5.1 DATA DEFINITION LANGUAGE, The Data Definition Language (DDL) consist of SQL statements used to define the, database structure or schema. It simply deals with descriptions of the database schema and is, used to create and modify the structure of database objects in databases., The DDL provides a set of definitions to specify the storage structure and access, methods used by the database system., 207, , Chapter 12.indd 207, , Structured Query Language, , 20-02-2019 15:30:40
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A DDL performs the following functions :, 1. It should identify the type of data division such as data item, segment, record and database, file., 2. It gives a unique name to each data item type, record type, file type and data base., 3. It should specify the proper data type., 4. It should define the size of the data item., 5. It may define the range of values that a data item may use., 6. It may specify privacy locks for preventing unauthorized data entry., SQL commands which comes under Data Definition Language are:, Create, , To create tables in the database., , Alter, , Alters the structure of the database., , Drop, , Delete tables from database., , Truncate Remove all records from a table, also release the space occupied by those records., , 12.5.2 DATA MANIPULATION LANGUAGE, A Data Manipulation Language (DML) is a computer programming language used, for adding (inserting), removing (deleting), and modifying (updating) data in a database., In SQL, the data manipulation language comprises the SQL-data change statements, which, modify stored data but not the schema of the database table., After the database schema has been specified and the database has been created, the, data can be manipulated using a set of procedures which are expressed by DML., By Data Manipulation we mean,, • Insertion of new information into the database, • Retrieval of information stored in a database., • Deletion of information from the database., • Modification of data stored in the database., , The DML is basically of two types:, Procedural DML – Requires a user to specify what data is needed and how to get it., Non-Procedural DML - Requires a user to specify what data is needed without, specifying how to get it., XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 208, , 208, , 20-02-2019 15:30:40
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SQL commands which comes under Data Manipulation Language are :, Insert, , Inserts data into a table, , Update, , Updates the existing data within a table., , Delete, , Deletes all records from a table, but not the space occupied by them., , 12.5.3 DATA CONTROL LANGUAGE, A Data Control Language (DCL) is a programming language used to control, the access of data stored in a database. It is used for controlling privileges in the database, (Authorization). The privileges are required for performing all the database operations such as, creating sequences, views of tables etc., SQL commands which come under Data Control Language are:, Grant, , Grants permission to one or more users to perform specific tasks., , Revoke, , Withdraws the access permission given by the GRANT statement., , 12.5.4 TRANSACTIONAL CONTROL LANGUAGE, Transactional control language (TCL) commands are used to manage transactions, in the database. These are used to manage the changes made to the data in a table by DML, statements., SQL command which come under Transfer Control Language are:, Commit, , Saves any transaction into the database permanently., , Roll back, , Restores the database to last commit state., , Save point Temporarily save a transaction so that you can rollback., , 12.5.5 DATA QUERY LANGUAGE, The Data Query Language consist of commands used to query or retrieve data from a, database. One such SQL command in Data Query Language is, Select :, , It displays the records from the table., , 12.6 Data Types, The data in a database is stored based on the kind of value stored in it. This is identified, as the data type of the data or by assigning each field a data type. All the values in a given field, must be of same type., , 209, , Chapter 12.indd 209, , Structured Query Language, , 20-02-2019 15:30:40
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The ANSI SQL standard recognizes only Text and Number data type, while some, commercial programs use other datatypes like Date and Time etc. The ANSI data types are, listed below in Table 12.1, Data Type, , Description, , char, (Character), , Fixed width string value. Values of this type is enclosed in single quotes., For ex. Anu’s will be written as ‘Anu’ ‘s’., , varchar, , Variable width character string. This is similar to char except the size of the, data entry vary considerably., , It represents a fractional number such as 15.12, 0.123 etc. Here the size, argument consist of two parts : precision and scale. The precision indicates, dec (Decimal) how many digits the number may have and the scale indicates the maximum, number of digits to the right of the decimal point. The size (5, 2) indicates, precision as 5 and scale as 2. The scale cannot exceed the precision., numeric, , It is same as decimal except that the maximum number of digits may not, exceed the precision argument., , int, (Integer), , It represents a number without a decimal point. Here the size argument is, not used., , smallint, , It is same as integer but the default size may be smaller than Integer., , float, , It represents a floating point number in base 10 exponential notation and, may define a precision up to a maximum of 64., , real, , It is same as float, except the size argument is not used and may define a, precision up to a maximum of 64., , double, , Same as real except the precision may exceed 64., Table 12.1, , 12.7 SQL Commands and their Functions, Tables are the only way to store data, therefore all the information has to be arranged in, the form of tables. The SQL provides a predetermined set of commands to work on databases., Keywords, , They have a special meaning in SQL. They are understood as instructions., , Commands, , They are instructions given by the user to the database also known as, statements., , Clauses, , They begin with a keyword and consist of keyword and argument., , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 210, , 210, , 20-02-2019 15:30:40
Page 217 : Arguments They are the values given to make the clause complete., 12.7.1 DDL Commands, CREATE TABLE Command, You can create a table by using the CREATE TABLE command. When a table is created,, its columns are named, data types and sizes are to be specified. Each table must have at least, one column. The syntax of CREATE TABLE command is :, CREATE TABLE <table-name>, (<column name><data type>[<size>], (<column name><data type>[<size>]……, );, Now let us use the above syntax to store some information about the students of a class, in a database, for this you first need to create table. To create a student table, let us take some, information related to students like admission number which we can use it in short form as, (admno), name of student (name), gender, age etc. of the student. Let us create a table having, the field names Admno, Name, Gender, Age and Place., The SQL command will be as follows:, CREATE TABLE Student, (Admno integer,, Name char(20),, Gender char(1),, Age integer,, Place char(10),, );, The above one is a simple table structure without any restrictions. You can also set, constraints to limit the type of data that can go into the fields of the table. Constraints are used, to limit the type of data that can go into a table. This ensures the accuracy and reliability of the, data in the database. Constraints could be either on a column level or a table level., Note, Constraint is a condition applicable on a field or set of fields., Column constraint:, , Column constraint apply only to individual column., , Table constraint :, , Table constraint apply to a group of one or more columns., , 211, , Chapter 12.indd 211, , Structured Query Language, , 20-02-2019 15:30:40
Page 218 : The syntax for a table created with constraint is given as below:, CREATE TABLE <table-name>, (<column name><data type>[<size>]<column constraint>,, (<column name><data type>[<size>]<column constraint>……, <table constraint>(<column name>,[<column name>….])….., );, Following is an example for student table with “NOT NULL” column constraint. This, constraint enforces a field to always contain a value., CREATE TABLE Student, (, Admno integer NOT NULL PRIMARY KEY, → Primary Key constraint, Name char(20)NOT NULL,, Gender char(1),, Age integer,, Place char(10),, );, The above command creates a table “student” in which the field Admno of integer type, is defined NOT NULL, Name of char type is defined as NOT NULL which means these two, fields must have values. The fields Gender, Age and Place do not have any constraints., , 12.7.2 Type of Constraints, Constraints ensure database integrity, therefore known as database integrity constraints., The different types of constraints are :, Unique Constraint, Constraint, , Primary Key Constraint, Default Constraint, Check Constraint, , (i)Unique Constraint, This constraint ensures that no two rows have the same value in the specified columns., For example UNIQUE constraint applied on Admno of student table ensures that no two, students have the same admission number and the constraint can be used as:, , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 212, , 212, , 20-02-2019 15:30:40
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CREATE TABLE Student, (, Admno integer NOT NULL UNIQUE, → Unique constraint, Name char (20) NOT NULL,, Gender char (1),, Age integer,, Place char (10),, );, The UNIQUE constraint can be applied only to fields that have also been declared as, NOT NULL., When two constraints are applied on a single field, it is known as multiple constraints. In, the above Multiple constraints NOT NULL and UNIQUE are applied on a single field Admno,, the constraints are separated by a space and at the end of the field definition a comma(,) is, added. By adding these two constraints the field Admno must take some value ie. will not be, NULL and should not be duplicated., , (ii) Primary Key Constraint, This constraint declares a field as a Primary key which helps to uniquely identify a, record. It is similar to unique constraint except that only one field of a table can be set as, primary key. The primary key does not allow NULL values and therefore a field declared as, primary key must have the NOT NULL constraint., Example showing Primary Key Constraint in the student table:, CREATE TABLE Student, (, Admno integer NOT NULL PRIMARY KEY, → Primary Key constraint, Name char(20)NOT NULL,, Gender char(1),, Age integer,, Place char(10),, );, In the above example the Admno field has been set as primary key and therefore will, help us to uniquely identify a record, it is also set NOT NULL, therefore this field value cannot, be empty., , (iii) DEFAULT Constraint, The DEFAULT constraint is used to assign a default value for the field. When no value, is given for the specified field having DEFAULT constraint, automatically the default value will, be assigned to the field., 213, , Chapter 12.indd 213, , Structured Query Language, , 20-02-2019 15:30:40
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Example showing DEFAULT Constraint in the student table:, CREATE TABLE Student, (, Admno integer NOT NULL PRIMARY KEY,, Name char(20)NOT NULL,, Gender char(1),, Age integer DEFAULT = “17”, → Default Constraint, Place char(10),, );, In the above example the “Age” field is assigned a default value of 17, therefore when no, value is entered in age by the user, it automatically assigns 17 to Age., (iv) Check Constraint, This constraint helps to set a limit value placed for a field. When we define a check, constraint on a single column, it allows only the restricted values on that field. Example, showing check constraint in the student table:, CREATE TABLE Student, (, Admno integer NOT NULL PRIMARY KEY, Name char(20)NOT NULL,, Gender char(1),, Age integer (CHECK<=19), → Check Constraint, Place char(10),, );, In the above example the check constraint is set to Age field where the value of Age, must be less than or equal to 19., Note, The check constraint may use relational and logical operators for condition., (v) TABLE CONSTRAINT, When the constraint is applied to a group of fields of the table, it is known as Table, constraint. The table constraint is normally given at the end of the table definition. Let us take, a new table namely Student1 with the following fields Admno, Firstname, Lastname, Gender,, Age, Place:, , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 214, , 214, , 20-02-2019 15:30:40
Page 221 : CREATE TABLE Student 1, (, Admno integer, NOT NULL,, Firstname char(20),, Lastname char(20),, Gender char(1),, Age integer,, Place char(10),, PRIMARY KEY (Firstname, Lastname) → Table constraint, );, In the above example, the two fields, Firstname and Lastname are defined as Primary, key which is a Table constraint., 12.7.3 DML COMMANDS, Once the schema or structure of the table is created, values can be added to the table., The DML commands consist of inserting, deleting and updating rows into the table., (i) INSERT command, The INSERT command helps to add new data to the database or add new records to the, table. The command is used as follows:, INSERT INTO <table-name> [column-list] VALUES (values);, INSERT INTO Student (Admno, Name, Gender, Age, Place), VALUES (100,’ Ashish’,’ M’, 17,’ Chennai’);, INSERT INTO Student (Admno, Name, Gender, Age, Place), VALUES (102, ‘Adarsh’, ‘M’, 18, ‘Delhi’);, Two new records are added to the table as shown below:, Admno Name Gender Age Placee, 100, Ashish, M, 17 Chennai, 101, Adarsh, M, 18, Delhi, The order of values must match the order of columns in the CREATE TABLE command., Specifying the column names is optional if data is to be added for all columns. The command, to add values into the student table can also be used in the following way:, INSERT INTO Student VALUES ( 102, ‘Akshith’, ‘M’, ‘17,’ ‘Bangalore’);, 102, , Akshith, , M, , 17, , Bangalore, , The above command inserts the record into the student table., To add data to only some columns in a record by specifying the column name and their data,, it can be done by:, 215, , Chapter 12.indd 215, , Structured Query Language, , 20-02-2019 15:30:40
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INSERT INTO Student(Admno, Name, Place) VALUES (103, ‘Ayush’, ‘Delhi’);, 103, , Ayush, , M, , 18, , Delhi, , The above command adds the following record with default values of ‘M’ for Gender and Age, as 18., INSERT INTO Student (Admno, Name, Place) VALUES (104, ‘Abinandh’, ‘Chennai’);, 104, , Abinandh, , M, , 18, , Chennai, , The student table will have the following data:, Admno, , Name, , Gender, , Age, , Place, , 100, 101, 102, 103, 104, , Ashish, Adarsh, Akshith, Ayush, Abinandh, , M, M, M, M, M, , 17, 18, 17, 18, 18, , Chennai, Delhi, Bangalore, Delhi, Chennai, , The fields that are not given in the INSERT command will take default values, if it is defined, for them, otherwise NULL value will be stored., In the INSERT command the fields that are omitted will have either default value, defined or NULL value., , (ii) DELETE COMMAND, The DELETE command permanently removes one or more records from the table. It, removes the entire row, not individual fields of the row, so no field argument is needed. The, DELETE command is used as follows :, DELETE FROM table-name WHERE condition;, For example to delete the record whose admission number is 104 the command is given, as follows:, DELETE FROM Student WHERE Admno=104;, 104, , Abinandh, , M, , 18, , Chennai, , The following record is deleted from the Student table., To delete all the rows of the table, the command is used as :, DELETE * FROM Student;, The table will be empty now and could be destroyed using the DROP command, (Discussed in section 12.7.4.3)., XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 216, , 216, , 20-02-2019 15:30:41
Page 223 : (iii) UPDATE COMMAND, The UPDATE command updates some or all data values in a database. It can update, one or more records in a table. The UPDATE command specifies the rows to be changed using, the WHERE clause and the new data using the SET keyword. The command is used as follows:, UPDATE <table-name> SET column-name = value, column-name = value,…, WHERE condition;, For example to update the following fields:, UPDATE Student SET Age = 20 WHERE Place = “Bangalore”;, The above command will change the age to 20 for those students whose place is “Bangalore”., The table will be as updated as below:, Admno, , Name, , Gender, , Age, , Place, , 100, , Ashish, , M, , 17, , Chennai, , 101, , Adarsh, , M, , 18, , Delhi, , 102, , Akshith, , M, , 20, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , To update multiple fields, multiple field assignment can be specified with the SET clause, separated by comma. For example to update multiple fields in the Student table, the command, is given as:, UPDATE Student SET Age=18, Place = ‘Chennai’ WHERE Admno = 102;, 102, , Akshith, , M, , 18, , Chennai, , The above command modifies the record in the following way., Admno, , Name, , Gender, , Age, , Place, , 100, , Ashish, , M, , 17, , Chennai, , 101, , Adarsh, , M, , 18, , Delhi, , 102, , Akshith, , M, , 18, , Chennai, , 103, , Ayush, , M, , 18, , Delhi, , 12.7.4 Some Additional DDL Commands:, (i) ALTER COMMAND, The ALTER command is used to alter the table structure like adding a column, renaming, the existing column, change the data type of any column or size of the column or delete the, column from the table. It is used in the following way :, ALTER TABLE <table-name> ADD <column-name><data type><size>;, 217, , Chapter 12.indd 217, , Structured Query Language, , 20-02-2019 15:30:41
Page 224 : To add a new column “Address” of type ‘char’ to the Student table, the command is used as, ALTER TABLE Student ADD Address char;, To modify existing column of table, the ALTER TABLE command can be used with MODIFY, clause like wise:, ALTER <table-name> MODIFY<column-name><data type><size>;, ALTER TABLE Student MODIFY Address char (25);, The above command will modify the address column of the Student table to now hold 25, characters., The ALTER command can be used to rename an existing column in the following way :, ALTER <table-name> RENAME old-column-name TO new-column-name;, For example to rename the column Address to City, the command is used as :, ALTER TABLE Student RENAME Address TO City;, The ALTER command can also be used to remove a column or all columns, for example, to remove a particular column, the DROP COLUMN is used with the ALTER TABLE to, remove a particular field, the command can be used as:, ALTER <table-name> DROP COLUMN <column-name>;, To remove the column City from the Student table, the command is used as :, ALTER TABLE Student DROP COLUMN City;, (ii) TRUNCATE command, The TRUNCATE command is used to delete all the rows from the table, the structure, remains and the space is freed from the table. The syntax for TRUNCATE command is:, TRUNCATE TABLE table-name;, For example to delete all the records of the student table and delete the table the SQL statement, is given as follows:, TRUNCATE TABLE Student;, The table Student is removed and the space is freed., (iii) DROP TABLE command, The DROP TABLE command is used to remove a table from the database. If you, drop a table, all the rows in the table is deleted and the table structure is removed from the, database. Once a table is dropped we cannot get it back, so be careful while using DROP, TABLE command. But there is a condition for dropping a table; it must be an empty table., XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 218, , 218, , 20-02-2019 15:30:41
Page 225 : Remove all the rows of the table using DELETE command. The DELETE command is already, explained., To delete all rows, the command is given as :, DELETE * FROM Student;, Once all the rows are deleted, the table can be deleted by DROP TABLE command in the, following way:, DROP TABLE table-name;, For example to delete the Student table:, DROP TABLE Student;, DELETE, TRUNCATE AND DROP statement:, DELETE, , The DELETE command deletes only the rows from the table based on, the condition given in the where clause or deletes all the rows from the, table if no condition is specified. But it does not free the space containing, the table., , TRUNCATE, , The TRUNCATE command is used to delete all the rows, the structure, remains in the table and free the space containing the table., , DROP, , The DROP command is used to remove an object from the database. If you, drop a table, all the rows in the table is deleted and the table structure is, removed from the database. Once a table is dropped we cannot get it back., , 12.7.5 DQL COMMAND– SELECT command, One of the most important tasks when working with SQL is to generate Queries and, retrieve data. A Query is a command given to get a desired result from the database table. The, SELECT command is used to query or retrieve data from a table in the database. It is used to, retrieve a subset of records from one or more tables. The SELECT command can be used in, various forms:, Syntax of SELECT command :, SELECT <column-list>FROM<table-name>;, • Table-name is the name of the table from which the information is retrieved., • Column-list includes one or more columns from which data is retrieved., For example to view only admission number and name of students from the Student table the, command is given as follows:, , 219, , Chapter 12.indd 219, , Structured Query Language, , 20-02-2019 15:30:41
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If the Student table has the following data:, Admno, , Name, , Gender, , Age, , Place, , 100, 101, 102, 103, 104, , Ashish, Adarsh, Akshith, Ayush, Abinandh, , M, M, M, M, M, , 17, 18, 17, 18, 18, , Chennai, Delhi, Bangalore, Delhi, Chennai, , 105, 106, 107, , Revathi, Devika, Hema, , F, F, F, , 19, 19, 17, , Chennai, Bangalore, Chennai, , SELECT Admno, Name FROM Student;, The above SELECT command will display the following data:, Admno Name, 100, 101, 102, 103, 104, 105, 106, 107, , Ashish, Adarsh, Akshith, Ayush, Abinandh, Revathi, Devika, Hema, , To view all the fields and rows of the table the SELECT command can be given as, SELECT * FROM STUDENT;, (i) DISTINCT Keyword, The DISTINCT keyword is used along with the SELECT command to eliminate, duplicate rows in the table. This helps to eliminate redundant data. For Example:, SELECT DISTINCT Place FROM Student;, Will display the following data as follows :, SELECT * FROM Student;, Place, Chennai, Bangalore, Delhi, In the above output you can see, there would be no duplicate rows in the place field., When the keyword DISTINCT is used, only one NULL value is returned, even if more NULL, values occur., XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 220, , 220, , 20-02-2019 15:30:41
Page 227 : (ii) ALL Keyword, The ALL keyword retains duplicate rows. It will display every row of the table without, considering duplicate entries., SELECT ALL Place FROM Student;, The above command will display all values of place field from every row of the table, without considering the duplicate entries., Place, Chennai, Delhi, Bangalore, Delhi, Chennai, Chennai, Bangalore, Chennai, The WHERE clause in the SELECT command specifies the criteria for getting the, desired result. The general form of SELECT command with WHERE Clause is:, SELECT <column-name>[,<column-name>,….] FROM <table-name>WHERE condition>;, , For example to display the students admission number and name of only those students who, belong to Chennai, the SELECT command is used in the following way :, SELECT Admno, Name, Place FROM Student WHERE Place =”Chennai”;, Admno, 100, 104, 105, 107, , Name, Ashish, Abinandh, Revathi, Hema, , Place, Chennai, Chennai, Chennai, Chennai, , SELECT Admno, Name, Age FROM Student WHERE Age >= 18;, Admno, 101, 103, 104, 105, 106, , Name, Adarsh, Ayush, Abinandh, Revathi, , Age, 18, 18, 18, 19, , Devika, , 19, , The relational operators like =, <, <=, >, >=, <> can be used to compare two values in, the SELECT command used with WHERE clause. The logical operaors OR, AND and NOT, 221, , Chapter 12.indd 221, , Structured Query Language, , 20-02-2019 15:30:41
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can also be used to connect search conditions in the WHERE clause. For example :, SELECT Admno, Name, Age, Place FROM Student WHERE (Age>=18 AND Place = "Delhi");, , Admno, Name, 101, Adarsh, 103, Ayush, , Place, Delhi, Delhi, , Age, 18, 18, , The SELECT command can also be used in the following ways:, SELECT Admno, Name, Age, Place FROM Student WHERE (Age>=18 OR Place ="Delhi");, SELECT Admno, Name, Place FROM Student WHERE (NOT Place ="Delhi");, (iii), , BETWEEN and NOT BETWEEN Keywords, , The BETWEEN keyword defines a range of values the record must fall into to make the, condition true. The range may include an upper value and a lower value between which the, criteria must fall into., SELECT Admno, Name, Age, Gender FROM Student WHERE Age BETWEEN 18 AND 19;, , Admno, , Name, , Gender, , Age, , Place, , 101, , Adarsh, , M, , 18, , Delhi, , 103, , Ayush, , M, , 18, , Delhi, , 104, , Abinandh, , M, , 18, , Chennai, , 105, , Revathi, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , The NOT BETWEEN is reverse of the BETWEEN operator where the records not satisfying, the condition are displayed., SELECT Admno, Name, Age FROM Student WHERE Age NOT BETWEEN 18 AND 19;, Admno, , Name, , Age, , 100, , Ashish, , 17, , 102, , Akshith, , 17, , 107, , Hema, , 17, , (iv) IN Keyword, The IN keyword is used to specify a list of values which must be matched with the, record values. In other words it is used to compare a column with more than one value. It is, similar to an OR condition., For example :, SELECT Admno, Name, Place FROM Student WHERE Place IN (“Chennai”, “Delhi”);, XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 222, , 222, , 20-02-2019 15:30:41
Page 229 : Admno, 100, 101, 103, 104, 105, 107, , Name, Ashish, Adarsh, Ayush, Abinandh, , Place, Chennai, Delhi, Delhi, Chennai, , Revathi, Hema, , Chennai, Chennai, , The NOT IN keyword displays only those records that do not match in the list., For example:, SELECT Admno, Name, Place FROM Student WHERE Place NOT IN (“Chennai”, “Delhi”);, will display students only from places other than “Chennai” and “Delhi”., Admno, 102, 106, , Name, Akshith, Devika, , Age, Bangalore, Bangalore, , NULL Value :, The NULL value in a field can be searched in a table using the IS NULL in the WHERE, clause. For example to list all the students whose Age contains no value, the command is used, as:, SELECT * FROM Student WHERE Age IS NULL;, Note, Non NULL values in a table can be listed using IS NOT NULL., (v) ORDER BY clause, The ORDER BY clause in SQL is used to sort the data in either ascending or descending, based on one or more columns., 1. By default ORDER BY sorts the data in ascending order., 2. We can use the keyword DESC to sort the data in descending order and the keyword ASC, to sort in ascending order., The ORDER BY clause is used as :, SELECT <column-name>[,<column-name>,….] FROM <table-name>ORDER, BY <column1>,<column2>,…ASC| DESC ;, , 223, , Chapter 12.indd 223, , Structured Query Language, , 20-02-2019 15:30:41
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For example :, To display the students in alphabetical order of their names, the command is used as, SELECT * FROM Student ORDER BY Name;, The above student table is arranged as follows :, Admno, , Name, , Gender, , Age, , Place, , 104, , Abinandh, , M, , 18, , Chennai, , 101, , Adarsh, , M, , 18, , Delhi, , 102, , Akshith, , M, , 17, , Bangalore, , 100, , Ashish, , M, , 17, , Chennai, , 103, , Ayush, , M, , 18, , Delhi, , 106, , Devika, , F, , 19, , Bangalore, , 107, , Hema, , F, , 17, , Chennai, , 105, , Revathi, , F, , 19, , Chennai, , Note, The ORDER BY clause does not affect the original table., (vi) WHERE clause, The WHERE clause is used to filter the records. It helps to extract only those records, which satisfy a given condition. For example in the student table, to display the list of students, of age18 and above in alphabetical order of their names, the command is given as below:, SELECT * FROM Student WHERE Age>=18 ORDER BY Name;, Admno, , Name, , Gender, , Age, , Place, , 104, , Abinandh, , M, , 18, , Chennai, , 101, , Adarsh, , M, , 18, , Delhi, , 103, , Ayush, , M, , 18, , Delhi, , 106, , Devika, , F, , 19, , Bangalore, , 105, , Revathi, , F, , 19, , Chennai, , To display the list of students in the descending order of names of those students of age, 18 and above the command is given as :, SELECT * FROM Student WHERE Age>=18 ORDER BY Name DESC;, , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 224, , 224, , 20-02-2019 15:30:41
Page 231 : Admno, , Name, , Gender, , Age, , Place, , 105, , Revathi, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , 101, , Adarsh, , M, , 18, , Delhi, , 104, , Abinandh, , M, , 18, , Chennai, , Note, Sorting can be done on multiple fields., (vii) GROUP BY clause, The GROUP BY clause is used with the SELECT statement to group the students on, rows or columns having identical values or divide the table in to groups. For example to know, the number of male students or female students of a class, the GROUP BY clause may be, used. It is mostly used in conjunction with aggregate functions to produce summary reports, from the database., The syntax for the GROUP BY clause is, SELECT <column-names> FROM <table-name> GROUP BY <column-name>HAVING, condition];, To apply the above command on the student table :, SELECT Gender FROM Student GROUP BY Gender;, The following command will give the below given result:, Gender, M, F, The point to be noted is that only two results have been returned. This is because we, only have two gender types ‘Male’ and ‘Female’. The GROUP BY clause grouped all the ‘M’, students together and returned only a single row for it. It did the same with the ‘F’ students., For example to count the number of male and female students in the student table, the, following command is given :, , 225, , Chapter 12.indd 225, , Structured Query Language, , 20-02-2019 15:30:41
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SELECT Gender, count(*) FROM Student GROUP BY Gender;, Gender, M, F, , count(*), 5, 3, , Note, The * is used with the COUNT to include the NULL values., The GROUP BY applies the aggregate functions independently to a series of groups that, are defined by having a field value in common. The output of the above SELECT statement, gives a count of the number of Male and Female students., (viii) HAVING clause, The HAVING clause can be used along with GROUP BY clause in the SELECT, statement to place condition on groups and can include aggregate functions on them. For, example to count the number of Male and Female students belonging to Chennai ., SELECT Gender , count(*) FROM Student GROUP BY Gender HAVING Place = ‘Chennai’;, Gender, M, , count(*), 2, , F, , 2, , The above output shows the number of Male and Female students in Chennai from the, table student., 12.7.6 TCL commands, (i) COMMIT command, The COMMIT command is used to permanently save any transaction to the database., When any DML commands like INSERT, UPDATE, DELETE commands are used, the, changes made by these commands are not permanent. It is marked permanent only after the, COMMIT command is given from the SQL prompt. Once the COMMIT command is given,, the changes made cannot be rolled back. The COMMIT command is used as, COMMIT;, (ii) ROLLBACK command, The ROLLBACK command restores the database to the last commited state. It is used, with SAVEPOINT command to jump to a particular savepoint location. The syntax for the, ROLLBACK command is :, ROLL BACK TO save point name;, XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 226, , 226, , 20-02-2019 15:30:41
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(iii) SAVEPOINT command, The SAVEPOINT command is used to temporarily save a transaction so that you, can rollback to the point whenever required. The different states of our table can be saved at, anytime using different names and the rollback to that state can be done using the ROLLBACK, command., SAVEPOINT savepoint_name;, Example showing COMMIT, SAVEPOINT and ROLLBACK in the student table, having the following data:, Admno, , Name, , Gender, , Age, , Place, , 105, , Revathi, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , 101, , Adarsh, , M, , 18, , Delhi, , 104, , Abinandh, , M, , 18, , Chennai, , INSERT INTO Student VALUES (107, 'Beena', 'F', 20 , 'Cochin');, COMMIT;, Admno, , Name, , Gender, , Age, , Place, , 105, 106, 103, 101, 104, , Revathi, Devika, Ayush, Adarsh, Abinandh, , F, F, M, M, M, , 19, 19, 18, 18, 18, , Chennai, Bangalore, Delhi, Delhi, Chennai, , 107, , Beena, , F, , 20, , Cochin, , UPDATE Student SET Name = ‘Mini’ WHERE Admno=105;, SAVEPOINT A;, Admno, , Name, , Gender, , Age, , Place, , 105, , Mini, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , 101, , Adarsh, , M, , 18, , Delhi, , 104, , Abinandh, , M, , 18, , Chennai, , 107, , Beena, , F, , 20, , Cochin, , 227, , Chapter 12.indd 227, , Structured Query Language, , 20-02-2019 15:30:41
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INSERT INTO Student VALUES(106, 'Jisha', 'F', 19, 'Delhi');, SAVEPOINT B;, Admno, , Name, , Gender, , Age, , Place, , 105, , Mini, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , 101, , Adarsh, , M, , 18, , Delhi, , 104, , vAbinandh, , M, , 18, , Chennai, , 107, , Beena, , F, , 20, , Cochin, , 108, , Jisha, , F, , 19, , Delhi, , ROLLBACK TO A;, Admno, , Name, , Gender, , Age, , Place, , 105, , Mini, , F, , 19, , Chennai, , 106, , Devika, , F, , 19, , Bangalore, , 103, , Ayush, , M, , 18, , Delhi, , 101, , Adarsh, , M, , 18, , Delhi, , 104, , Abinandh, , M, , 18, , Chennai, , 107, , Beena, , F, , 20, , Cochin, , Points to remember:, •, , SQL is a language that helps to create and operate relational databases., , •, , MySQL is a database management system., , • The various components of SQL are Data Definition Language (DDL), Data, Manipulation Language (DML), Data Query Language (DQL), Transactional, Control Language (TCL), Data Control Language (DCL)., • The DDL provides statements for creation and deletion of tables., • The DML provides statements to insert, update and delete data of a table., • The DCL provides authorization commands to access data., • The TCL commands are used to manage transactions in a database., • The DQL commands help to generate queries in a database., • The CREATE TABLE command creates a new table., , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 228, , 228, , 20-02-2019 15:30:41
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Points to remember:, •, , SQL is a language that helps to create and operate relational databases., , •, , MySQL is a database management system., , • The various components of SQL are Data Definition Language (DDL), Data, Manipulation Language (DML), Data Query Language (DQL), Transactional, Control Language (TCL), Data Control Language (DCL)., • The DDL provides statements for creation and deletion of tables., • The DML provides statements to insert, update and delete data of a table., • The DCL provides authorization commands to access data., • The TCL commands are used to manage transactions in a database., • The DQL commands help to generate queries in a database., • The CREATE TABLE command creates a new table., , Hands on Experience, 1., , Create a query of the student table in the following order of fields name, age, place and, admno., , 2., , Create a query to display the student table with students of age more than 18 with unique, city., , 3. Create a employee table with the following fields employee number, employee name,, designation, date of joining and basic pay., 4. In the above table set the employee number as primary key and check for NULL values in, any field., 5. Prepare a list of all employees who are Managers., , 229, , Chapter 12.indd 229, , Structured Query Language, , 20-02-2019 15:30:41
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Evaluation, Part - I, , Choose the best answer, 1., , 2., , 3., , 4., , 5., , (1 Marks), , Which commands provide definitions for creating table structure, deleting relations, and, modifying relation schemas., a. DDL, , b. DML, , c. DCL, , d. DQL, , Which command lets to change the structure of the table?, a. SELECT, , b. ORDER BY, , c. MODIFY, , d. ALTER, , The command to delete a table is, A) DROP, , B) DELETE, , C) DELETE ALL, , D) ALTER TABLE, , Queries can be generated using, a. SELECT, , b. ORDER BY, , c. MODIFY, , d. ALTER, , The clause used to sort data in a database, a. SORT BY, , b. ORDER BY, , c. GROUP BY, , d. SELECT, Part -II, , Answer the following questions, , (2 Marks), , 1. Write a query that selects all students whose age is less than 18 in order wise., 2. Differentiate Unique and Primary Key constraint., 3. Write the difference between table constraint and column constraint?, 4. Which component of SQL lets insert values in tables and which lets to create a table?, 5. What is the difference between SQL and MySQL?, , XII, XII Std, Std Computer, Computer Science, Science, , Chapter 12.indd 230, , 230, , 20-02-2019 15:30:41
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Part -III, , Answer the following questions, , (3 Marks), , 1. What is a constraint? Write short note on Primary key constraint., 2. Write a SQL statement to modify the student table structure by adding a new field., 3. Write any three DDL commands., 4. Write the use of Savepoint command with an example., 5. Write a SQL statement using DISTINCT keyword., Part -IV, , Answer the following questions, , (5 Marks), , 1. Write the different types of constraints and their functions., 2. Consider the following employee table. Write SQL commands for the qtns.(i) to (v)., EMP CODE, S1001, P1002, P1003, C1004, M1005, (i), , NAME, Hariharan, Shaji, Prasad, Manjima, Ratheesh, , DESIG, Supervisor, Operator, Operator, Clerk, Mechanic, , PAY, 29000, 10000, 12000, 8000, 20000, , ALLO WANCE, 12000, 5500, 6500, 4500, 7000, , To display the details of all employees in descending order of pay., , (ii) To display all employees whose allowance is between 5000 and 7000., (iii) To remove the employees who are mechanic., (iv) To add a new row., (v), , To display the details of all employees who are operators., , 3., , What are the components of SQL? Write the commands in each., , 4., , Construct the following SQL statements in the student table(i), , SELECT statement using GROUP BY clause., , (ii) SELECT statement using ORDER BY clause., 5., , Write a SQL statement to create a table for employee having any five fields and create a, table constraint for the employee table., , 231, , Chapter 12.indd 231, , Structured Query Language, , 20-02-2019 15:30:41
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Unit, , CHAPTER 13, , IV, , PYTHON AND CSV FILES, , Learning Objectives, After the completion of this chapter, the student will be able to, • Understand what is CSV?, • Able to import CSV files in python programs., • Execute and debug python programs., , 13.1 Introduction, Python has a vast library of modules that are included with its distribution. One among, the module is the CSV module which gives the Python programmer the ability to parse CSV, (Comma Separated Values) files. A CSV file is a human readable text file where each line, has a number of fields, separated by commas or some other delimiter. You can assume each, line as a row and each field as a column. The CSV module will be able to read and write the vast, majority of CSV files., , 13.2 Difference between CSV and XLS file formats, The difference between Comma-Separated Values (CSV) and eXceL Sheets(XLS) file, formats is, Excel, Excel is a binary file that holds information, about all the worksheets in a file, including, both content and formatting, , CSV, CSV format is a plain text format with a, series of values separated by commas., , XLS files can only be read by applications, that have been especially written to read their, format, and can only be written in the same, way., , CSV can be opened with any text editor, in Windows like notepad, MS Excel,, OpenOffice, etc., , Excel is a spreadsheet that saves files into its, own proprietary format viz. xls or xlsx, , CSV is a format for saving tabular, information into a delimited text file with, extension .csv, , Excel consumes more, importing, data, , Importing CSV files can be much faster, and, it also consumes less memory, , XII Std Computer Science, , Chapter 13.indd 232, , memory, , while, , 232, 232, , 20-02-2019 15:33:05
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Files saved in excel cannot be opened or edited by text editors., , 13.3 Purpose Of CSV File, CSV is a simple file format used to store tabular data, such as a spreadsheet or database., Since they're plain text, they're easier to import into a spreadsheet or another storage database,, regardless of the specific software you're using., You can open CSV files in a spreadsheet program like Microsoft Excel or in a text editor, or through a database which make them easier to read., Note, CSV File cannot store charts or graphs. It stores data but does not contain, formatting, formulas, macros, etc., A CSV file is also known as a Flat File. Files in the CSV format can be, imported to and exported from programs that store data in tables, such as Microsoft, Excel or OpenOfficeCalc, , 13.4 Creating a CSV file using Notepad (or any text editor), A CSV file is a text file, so it can be created and edited using any text editor, But more, frequently a CSV file is created by exporting a spreadsheet or database in the program that, created it., 13.4.1 Creating CSV Normal File, To create a CSV file in Notepad, First open a new file using, File →New or ctrl +N., Then enter the data you want the file to contain, separating each value with a comma, and each row with a new line., For example consider the following details, Topic1,Topic2,Topic3, one,two,three, Example1,Example2,Example3, Save this content in a file with the extension .csv . You can then open the same using, Microsoft Excel or any other spreadsheet program. Here we have opened using Microsoft, Excel. It would create a table of data similar to the following:, 233, , Chapter 13.indd 233, , Python and CSV files, , 20-02-2019 15:33:05
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Topic1, , Topic2, , Topic3, , one, , two, , three, , Example1, , Example2, , Example3, , Fig. 13.1 CSV file when opened in MS-Excel, In the above CSV file, you can observe the fields of data were separated by commas. But, what happens if the data itself contains commas in it?, If the fields of data in your CSV file contain commas, you can protect them by enclosing, those data fields in double-quotes (“). The commas that are part of your data will then be kept, separate from the commas which delimit the fields themselves., 13.4.2 Creating CSV File That contains Comma With Data, For example, let’s say that one of our fields contain commas in the description. If our, data looked like the below example:, RollNo, , Name, , Address, , 12101, , Nivetha, , Mylapore, Chennai, , 12102, , Lavanya, , Adyar, Chennai, , 12103, , Ram, , Gopalapuram,, Chennai, , To retain the commas in “Address” column, you can enclose the fields in quotation, marks. For example:, RollNo, Name, Address, 12101, Nivetha, “Mylapore, Chennai”, 12102, Lavanya, “Adyar, Chennai”, 12103, Ram, “Gopalapuram, Chennai”, , XII Std Computer Science, , Chapter 13.indd 234, , 234, 234, , 20-02-2019 15:33:06
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As you can see, only the fields that contain commas are enclosed in quotes. If you open, this in MS Excel, It looks like as follows, , Roll No, , Name, , Address, , 12101, , Nivetha, , Mylapore, Chennai, , 12102, , Lavanya, , Adyar, Chennai, , 12102, , Ram, , Gopalapuram, Chennai, , Fig 13.2 CSV Field data with comma in Excel, The same goes for newlines which may be part of your field data. Any fields containing, a newline as part of its data need to be enclosed in double-quotes., For Example, RollNo Name, Address, 12101 Nivetha Mylapore, Chennai, 12102 Lavanya Adyar, Chennai, 12103 Ram, Gopalapuram, Chennai, It should be written in CSV file as, RollNo, Name, Address, 12101, Nivetha, “Mylapore, Chennai”, 12102, Lavanya, “Adyar, Chennai”, 12103, Ram, “Gopalapuram, Chennai”, The Result will look like this, , 235, , Chapter 13.indd 235, , Python and CSV files, , 20-02-2019 15:33:06
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Roll No, , Name, , Address, , 12101, , Nivetha, , Mylapore,, Chennai, , 12102, , Lavanya, , Adyar,, Chennai, , 12102, , Ram, , Gopalapuram,, Chennai, , Fig 13.3 CSV Field Data with newline in Excel, 13.4.3 Creating CSV File That contains Double Quotes With Data, If your fields contain double-quotes as part of their data, the internal quotation, marks need to be doubled so that they can be interpreted correctly. For Example, given the, following data:, Roll No, , Name, , Favorite Sports, , Address, , 12101, , Nivetha, , “Cricket”, “Football”, , Mylapore Chennai, , 12102, , Lavanya, , “Basketball”, “Cricket”, , Adyar Chennai, , 12103, , Ram, , “Soccer”, “Hockey”, , Gopala puram Chennai, , It should be written in csv file as, RollNo, Name, FavoriteSports, Address, 12101, Nivetha,””” Cricket ””,”” Football ”””, Mylapore chennai 12102, Lavanya,””” Basketball, ””,”” Cricket ”””, Adyar hennai 12103, Ram,””” Soccer””,”” Hockey”””, Gopalapuram, chennai, The output will be, , XII Std Computer Science, , Chapter 13.indd 236, , 236, 236, , 20-02-2019 15:33:06
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Roll No, 12101, 12102, 12103, , Name, , Favorite Sports, , Address, , Nivetha, Lavanya, , "Cricket", "Football", "Basketball", "Cricket", "Soccer", "Hockey", , Mylapore, Chennai, Adyar, Chennai, , Ram, , Gopalapuram, Chennai, , Fig 13.4 CSV Field Data with Double quotes in Excel, 13.4.4 Rules to be followed to format data in a CSV file, 1., , Each record (row of data) is to be located on a separate line, delimited by a line break by, pressing enter key. For example:, xxx,yyy, denotes enter Key to be pressed, , 2., , The last record in the file may or may not have an ending line break. For example:, ppp, qqq, yyy, xxx, , 3., , There may be an optional header line appearing as the first line of the file with the same, format as normal record lines. The header will contain names corresponding to the fields, in the file and should contain the same number of fields as the records in the rest of the, file. For example: field_name1,field_name2,field_name3, aaa,bbb,ccc, zzz,yyy,xxx CRLF( Carriage Return and Line Feed), 237, , Chapter 13.indd 237, , Python and CSV files, , 20-02-2019 15:33:06
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4., , Within the header and each record, there may be one or more fields, separated by commas., Spaces are considered part of a field and should not be ignored. The last field in the record, must not be followed by a comma. For example: Red , Blue, , 5., , Each field may or may not be enclosed in double quotes. If fields are not enclosed with, double quotes, then double quotes may not appear inside the fields. For example:, , 6., , "Red","Blue","Green", , #Field data with doule quotes, , Black,White,Yellow , , #Field data without doule quotes, , Fields containing line breaks (CRLF), double quotes, and commas should be enclosed in, double-quotes. For example:, Red, “,”, Blue CRLF # comma itself is a field value.so it is enclosed with double quotes, Red, Blue , Green, , 7., , If double-quotes are used to enclose fields, then a double-quote appearing inside a field, must be preceded with another double quote. For example:, “Red, ” “Blue”, “Green”,, , # since double quotes is a field value it is enclosed with another double quotes, , , , White, Note, The last row in the above example begins with two commas because the first two, fields of that row were empty in our spreadsheet. Don't delete them — the two commas, are required so that the fields correspond from row to row. They cannot be omitted., , 13.5 Create A CSV File Using Microsoft Excel, To create a CSV file using Microsoft Excel, launch Excel and then open the file you, want to save in CSV format. For example, below is the data contained in our sample Excel, worksheet:, , XII Std Computer Science, , Chapter 13.indd 238, , 238, 238, , 20-02-2019 15:33:06
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Item Name, , Cost - Rs, , Keyboard, , 480, 5200, 200, , Quantity, , Profit, , 12, , 1152, , 10400, 2000, Total Prof 13552, 10, 50, , Fig 13.5 Sample Worksheet Data, Once the data is entered in the worksheet, select File → Save As option, and for the, “Save as type option”, select CSV (Comma delimited) or type the file name along with extension, .csv., Saving excel file as CSV, , Fig 13.6 Save As dialog box, After you save the file, you are free to open it up in a text editor to view it or to edit it, manually. Its contents will resemble the following:, , 239, , Chapter 13.indd 239, , Python and CSV files, , 20-02-2019 15:33:06
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Item Name, Cost-Rs, Quantity, Profit, Keyboard, 480, 12, 1152, Monitor, 5200, 10, 10400, Mouse, 200, 50, 2000, ,,Total Profit =,13552, 13.5.1 Microsoft Excel to open a CSV file, If Microsoft Excel has been installed on the computer, by default CSV files should, open automatically in Excel when the file is double-clicked. If you are getting an Open With, prompt when opening the CSV file, choose Microsoft Excel from the available programs to, open the file., Alternatively, you can open Microsoft Excel and in the menu bar, select File → Open,, and select the CSV file. If the file is not listed, make sure to change the file type to be opened, to Text Files (*.prn, *.txt, *.csv)., If both MS Excel and Open Office calc is installed in the computer, by, default the CSV file will be opened in MS Excel., , 13.6 Read and write a CSV file Using Python, Python provides a module named CSV, using this you can do several operations on the, CSV files. The CSV library contains objects and other code to read, write, and process data, from and to CSV files., CSV files have been used extensively in e-commerce applications because, they are considered very easy to process., 13.6.1 Read a CSV File Using Python, There are two ways to read a CSV file., 1. Use the csv module’s reader function, 2. Use the DictReader class., Two ways of Reading CSV File, , reader () function, , Dict Reader class, , Fig 13.7 Ways to read CSV file, XII Std Computer Science, , Chapter 13.indd 240, , 240, 240, , 20-02-2019 15:33:06
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When you want to read from or write to a file ,you need to open it. Once the reading, is over it needs to be closed. So that, resources that are tied with the file are freed. Hence, in, Python, a file operation takes place in the following order, Step 1, , Open a file, , Step 2, , Perform Read or write operation, , Step 3, , Close the file, , Note, File name or the complete path name can be represented either with in “ “ or in ‘ ‘, in the open command., Python has a built-in function open() to open a file. This function returns a file, object, also called a handle, as it is used to read or modify the file accordingly., For Example, >>> f = open("sample.txt") # open file in current directory and f is file object, >>> f = open('c:\\pyprg\\ch13sample5.csv'), , # specifying full path, , You can specify the mode while opening a file. In mode, you can specify whether you, want to read 'r', write 'w' or append 'a' to the file. you can also specify “text or binary” in which, the file is to be opened., The default is reading in text mode. In this mode, while reading from the file the data, would be in the format of strings., On the other hand, binary mode returns bytes and this is the mode to be used when, dealing with non-text files like image or exe files., Python File Modes, Mode, , Description, , 'r', , Open a file for reading. (default), , 'w', , Open a file for writing. Creates a new file if it does not exist or truncates the file if, it exists., , 'x', , Open a file for exclusive creation. If the file already exists, the operation fails., , 241, , Chapter 13.indd 241, , Python and CSV files, , 20-02-2019 15:33:06
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'a', , Open for appending at the end of the file without truncating it. Creates a new file, if it does not exist., , 't', , Opren in text mode. (default), , 'b', , Open in binary mode., , '+', , Open a file for updating (reading and writing), , f=open("sample.txt"), #equivalent to 'r' or 'rt', f = open("sample.txt",'w') , , # write in text mode, , f = open("image1.bmp",'r+b') , , # read and write in binary mode, , Python has a garbage collector to clean up unreferenced objects but, one must not, rely on it to close the file., f = open("test.txt") , # perform file operations, f.close(), , # since no mode is specified the default mode rt is used, , The above method is not entirely safe. If an exception occurs when you are performing, some operation with the file, the code exits without closing the file. The best way to do this is, using the “with” statement. This ensures that the file is closed when the block inside with is, exited. You need not to explicitly call the close() method. It is done internally., with open("test.txt",’r’) as f:, # f is file object to perform file operations, Closing a file will free up the resources that were tied with the file and is done using, Python close() method., f = open("sample.txt"), # perform file operations, f.close(), (i) CSV Module’s Reader Function, You can read the contents of CSV file with the help of csv.reader() method. The reader, function is designed to take each line of the file and make a list of all columns. Then, you, just choose the column you want the variable data for. Using this method one can read data, from csv files of different formats like quotes (" "), pipe (|) and comma (,)., The syntax for csv.reader() is, XII Std Computer Science, , Chapter 13.indd 242, , 242, 242, , 20-02-2019 15:33:07
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csv.reader(fileobject,delimiter,fmtparams), where, file object :- passes the path and the mode of the file, delimiter :- an optional parameter containing the standard dilects like , | etc can be omitted, fmtparams: optional parameter which help to override the default values of the dialects like, skipinitialspace,quoting etc. Can be omitted, 1, 2, 3, 4, , CSV file - data with default delimiter comma (,), CSV file - data with Space at the beginning, CSV file - data with quotes, CSV file - data with custom Delimiters, , (a) CSV file with default delimiter comma (,), The following program read a file called “sample1.csv” with default delimiter comma (,), and print row by row., #importing csv, import csv, #opening the csv file which is in different location with read mode, with open('c:\\pyprg\\sample1.csv', 'r') as F:, #other way to open the file is f= ('c:\\pyprg\\sample1.csv', 'r'), reader = csv.reader(F), # printing each line of the Data row by row, print(row), F.close(), OUTPUT, ['SNO', 'NAME', 'CITY'], ['12101', 'RAM', 'CHENNAI'], ['12102', 'LAVANYA', 'TIRUCHY'], ['12103', 'LAKSHMAN', 'MADURAI'], (b) CSV files- data with Spaces at the beginning, Consider the following file “sample2.csv” containing the following data when opened, through notepad, Topic1,, one,, Example1,, , Topic2,, two,, , three, , Example2,, , Example3, , 243, , Chapter 13.indd 243, , Topic3,, , Python and CSV files, , 20-02-2019 15:33:07
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Note, A dialect is a class of csv module which helps to define parameters for, reading and writing CSV. It allows you to create, store, and re-use various formatting, parameters for your data., (c) CSV File-Data With Quotes, You can read the csv file with quotes, by registering new dialects using csv.register_dialect(), class of csv module., Here, we have quotes.csv file with following data., SNO,Quotes, 1, "The secret to getting ahead is getting started.", 2, "Excellence is a continuous process and not an accident.", 3, "Work hard dream big never give up and believe yourself.", 4, "Failure is the opportunity to begin again more intelligently.", 5, "The successful warrior is the average man, with laser-like focus.", The following Program read “quotes.csv” file, where delimiter is comma (,) but the, quotes are within quotes (“ “)., import csv, csv.register_dialect('myDialect',delimiter = ',',quoting=csv.QUOTE_ALL,, skipinitialspace=True), f=open('c:\\pyprg\\quotes.csv','r'), reader = csv.reader(f, dialect='myDialect'), for row in reader:, print(row), OUTPUT, ['SNO', 'Quotes'], ['1', 'The secret to getting ahead is getting started.'], ['2', 'Excellence is a continuous process and not an accident.'], ['3', 'Work hard dream big never give up and believe yourself.'], ['4', 'Failure is the opportunity to begin again more intelligently.'], ['5', 'The successful warrior is the average man, with laser-like focus. '], In the above program, register a dialect with name myDialect. Then, we used csv., QUOTE_ALL to display all the characters after double quotes., , 245, , Chapter 13.indd 245, , Python and CSV files, , 20-02-2019 15:33:07
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(d) CSV files with Custom Delimiters, You can read CSV file having custom delimiter by registering a new dialect with the, help of csv.register_dialect()., In the following file called “sample4.csv”,each column is separated with | (Pipe symbol), Roll No, 12101, 12102, 12103, 103, 104, , Name, Arun, Meena, Ram, Ayush, Abinandh, , City, Chennai, Kovai, Nellai, M, M, , The following program read the file “sample4.csv” with user defined delimiter “|”, import csv, csv.register_dialect('myDialect', delimiter = '|'), with open('c:\\pyprg\\sample4.csv', 'r') as f:, reader = csv.reader(f, dialect='myDialect'), for row in reader:, print(row), f.close(), , OUTPUT, ['RollNo', 'Name', 'City'], ['12101', 'Arun', 'Chennai'], ['12102', 'Meena', 'Kovai'], ['12103', 'Ram', 'Nellai'], , In the above program, a new dialects called myDialect is registered. Use the delimiter=|, where a pipe (|) is considered as column separator., 13.6.2 Read a specific column In a File, To get the specific columns like only Item Name and profit for the “sample5.csv” file ., Then you have to do the following:, import csv, #opening the csv file which is in different location with read mode, f=open("c:\\pyprg\\ch13sample5.csv",'r'), #reading the File with the help of csv.reader(), readFile=csv.reader(f), #printing the selected column, for col in readFile :, print col[0],col[3], f.close(), sample5.csv File in Excel, , XII Std Computer Science, , Chapter 13.indd 246, , 246, 246, , 20-02-2019 15:33:07
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A, , B, , C, , D, , 1 item Nam Cost-Rs, , Quantity Profit, , 2 Keyboard 480, , 12, , 1152, , 3 Monitor, , 5200, , 10, , 10400, , 4 Mouse, , 200, , 50, , 2000, , sample5.csv File with selected col, OUTPUT, Item Name Profit, Keyboard 1152, Monitor 10400, Mouse 2000, 13.6.3 Read A CSV File And Store It In A List, In this topic you are going to read a CSV file and the contents of the file will be stored, as a list. The syntax for storing in the List is, list = [] , list.append(element) , , # Start as the empty list, # Use append() to add elements, , For example all the row values of “sample.csv” file is stored in a list using the following, program, import csv, # other way of declaring the filename, inFile= 'c:\\pyprg\\sample.csv', F=open(inFile,'r'), reader = csv.reader(F), # declaring array, arrayValue = [], # displaying the content of the list, for row in reader:, arrayValue.append(row), print(row), F.close(), sample.csv opened in MS-Excel, , 247, , Chapter 13.indd 247, , Python and CSV files, , 20-02-2019 15:33:07
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2, 3, 4, , >, , 1, , A1, A, Topic 1, , B, Topic 2, , One, two, Example 1 Example 2, , fx Topic 1, C, Topic 3, three, Example 3, , sample5.csv File with selected col, OUTPUT, ['Topic1', 'Topic2', 'Topic3'], [' one', 'two', 'three'], ['Example1', 'Example2', 'Example3'], , Note, A list is a data structure in Python that is a mutable, or changeable,, ordered sequence of elements., List literals are written within square brackets [ ]. Lists work similarly to strings, , 13.6.4 Read A CSV File And Store A Column Value In A List For Sorting, In this program you are going to read a selected column from the “sample6.csv” file by, getting from the user the column number and store the content in a list., , XII Std Computer Science, , Chapter 13.indd 248, , 248, 248, , 20-02-2019 15:33:07
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Item Name, Keyboard, Monitor, , Cost - Rs Quantity Profit, 480, 12, 1152, 10400, 5200, 10, 200, 2000, 50, Total Prof, , 13552, , Fig 13.6.4 CSV file Data for a selected column for sorting, Since the row heading is also get sorted, to avoid that the first row should be skipped., This is can be done by using the command “next()”. The list is sorted and displayed., # sort a selected column given by user leaving the header column, import csv, # other way of declaring the filename, inFile= ‘c:\\pyprg\\sample6.csv’, # openning the csv file which is in the same location of this, , 249, , Chapter 13.indd 249, , Python and CSV files, , 20-02-2019 15:33:07
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python file, F=open(inFile,’r’), # reading the File with the help of csv.reader(), reader = csv.reader(F), # skipping the first row(heading), next(reader), # declaring a list, arrayValue = [], a = int(input (“Enter the column number 1 to 3:-“)), # sorting a particular column-cost, for row in reader:, arrayValue.append(row[a]), arrayValue.sort(), for row in arrayValue:, print (row), F.close(), OUTPUT, Enter the column number 1 to 3:- 2, 50, 12, 10, , Read a specific column in a csv file and display its result in Descending, (Reverse) order., list_name.sort() command arranges a list value in ascending order. list_name., sort(reverse) is used to arrange a list in descending order., 13.6.5 Sorting A CSV File With A Specified Column, In this program you are going to see the “sample8.csv” file’s entire content is transferred, to a list. Then the list of rows is sorted and displayed in ascending order of quantity. To sort, by more than one column you can use itemgetter with multiple indices: operator .itemgetter, (1,2), The content of “sample8.csv” is, , XII Std Computer Science, , Chapter 13.indd 250, , 250, 250, , 20-02-2019 15:33:07
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sample8.csv in Excel screen, , Item Name, Keyboard, Monitor, Mouse, , ItemName ,Quantity, Keyboard, 48, Monitor,52, Mouse ,20, , Quantity, 48, 52, 20, , sample8.csv in Notepad, , Fig 13.6.5 CSV file Data into a list for sorting, The following program do the task mentioned above using operator.itemgetter(col_no), #Program to sort the entire row by using a specified column., # declaring multiple header files, import csv ,operator, #One more way to read the file, data = csv.reader(open(‘c:\\PYPRG\\sample8.csv’)), next(data) #(to omit the header), #using operator module for sorting multiple columns, sortedlist = sorted (data, key=operator.itemgetter(1)) # 1 specifies we want to sort, # according to second column, for row in sortedlist:, print(row), OUTPUT, [‘Mouse ‘, ‘20’], [‘Keyboard ‘, ‘48’], [‘Monitor’, ‘52’], 251, , Chapter 13.indd 251, , Python and CSV files, , 20-02-2019 15:33:07
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Note, The sorted() method sorts the elements of a given item in a specific order –, Ascending or Descending. Sort() method which performs the same way as sorted()., Only difference, sort() method doesn’t return any value and changes the original list, itself., , Add one more column “cost” in “sample8.csv” and sort it in descending order, of cost by using the syntax, sortedlist = sorted(data, key=operator.itemgetter(Col_number),reverse=True), , 13.6.6 Reading CSV File Into A Dictionary, To read a CSV file into a dictionary can be done by using DictReader class of csv, module which works similar to the reader() class but creates an object which maps data to a, dictionary. The keys are given by the fieldnames as parameter. DictReader works by reading, the first line of the CSV and using each comma separated value in this line as a dictionary key., The columns in each subsequent row then behave like dictionary values and can be accessed, with the appropriate key (i.e. fieldname)., If the first row of your CSV does not contain your column names, you can pass a, fieldnames parameter into the DictReader’s constructor to assign the dictionary keys manually., The main difference between the csv.reader() and DictReader() is in simple terms csv., reader and csv.writer work with list/tuple, while csv.DictReader and csv.DictWriter work with, dictionary. csv.DictReader and csv.DictWriter take additional argument fieldnames that are, used as dictionary keys., For Example Reading “sample8.csv” file into a dictionary, import csv, filename = ‘c:\\pyprg\\sample8.csv’, input_file =csv.DictReader(open(filename,’r’)), for row in input_file:, print(dict(row)) , #dict() to print data, OUTPUT, {‘ItemName ‘: ‘Keyboard ‘, ‘Quantity’: ‘48’}, {‘ItemName ‘: ‘Monitor’, ‘Quantity’: ‘52’}, {‘ItemName ‘: ‘Mouse ‘, ‘Quantity’: ‘20’}, In the above program, DictReader() is used to read “sample8.csv” file and map into, a dictionary. Then, the function dict() is used to print the data in dictionary format without, order., XII Std Computer Science, , Chapter 13.indd 252, , 252, 252, , 20-02-2019 15:33:08
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Remove the dict() function from the above program and use print(row).Check, you are getting the following output, OrderedDict([(‘ItemName ‘, ‘Keyboard ‘), (‘Quantity’, ‘48’)]), OrderedDict([(‘ItemName ‘, ‘Monitor’), (‘Quantity’, ‘52’)]), OrderedDict([(‘ItemName ‘, ‘Mouse ‘), (‘Quantity’, ‘20’)]), , 13.6.7 Reading CSV File With User Defined Delimiter Into A Dictionary, You can also register new dialects and use it in the DictReader() methods. Suppose, “sample8.csv” is in the following format, ItemName, Keyboard, Monitor, Mouse, , Quantity, 48, 52, 20, , Then “sample8.csv” can be read into a dictionary by registering a new dialect, import csv, csv.register_dialect(‘myDialect’,delimiter = ‘|’,skipinitialspace=True), filename = ‘c:\\pyprg\\ch13\\sample8.csv’, with open(filename, ‘r’) as csvfile:, reader = csv.DictReader(csvfile, dialect=’myDialect’), for row in reader:, print(dict(row)), csvfile.close(), OUTPUT, {‘ItemName ,Quantity’: ‘Keyboard ,48’}, {‘ItemName ,Quantity’: ‘Monitor,52’}, {‘ItemName ,Quantity’: ‘Mouse ,20’}, Note, DictReader() gives OrderedDict by default in its output. An OrderedDict is a, dictionary subclass which saves the order in which its contents are added. To remove the, OrderedDict use dict()., , 13.7 Writing Data Into Different Types in Csv Files, As you know Python provides an easy way to work with CSV file and has csv module, to read and write data in the csv file. In the previous topics, You have learned how to read CSV, files in Python. In similar way, You can also write a new or edit an existing CSV files in Python., 253, , Chapter 13.indd 253, , Python and CSV files, , 20-02-2019 15:33:08
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1, 2, 3, 4, 5, 6, 7, 8, , Creating A New Normal CSV File, Modifying An Existing File, Writing On A CSV File with Quotes, Writing On A CSV File with Custom Delimiters, Writing On A CSV File with Lineterminator, Writing On A CSV File with Quotechars, Writing CSV File Into A Dictionary, Getting Data At Runtime And Writing In a File, , 13.7.1 Creating A New Normal CSV File, When you have a set of data that you would like to store inside a CSV file, it’s time to do, the opposite and use the write function., The csv.writer() method returns a writer object which converts the user’s data into, delimited strings on the given file-like object. The writerow() method writes a row of data, into the specified file., The syntax for csv.writer() is, csv.writer(fileobject,delimiter,fmtparams), where, fileobject, , : passes the path and the mode of the file., , delimiter, , : an optional parameter containing the standard dilects like , | etc can, be omitted., , fmtparams : optional parameter which help to override the default values of the, dialects like skipinitialspace,quoting etc. can be omitted., You can create a normal CSV file using writer() method of csv module having, default delimiter comma (,), Here’s an example., The following Python program converts a List of data to a CSV file called “Pupil.csv”, that uses, (comma) as a value separator., , XII Std Computer Science, , Chapter 13.indd 254, , 254, 254, , 20-02-2019 15:33:08
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Import csv, csvData = [[‘Student’, ‘Age’], [‘Dhanush’, ‘17’], [‘Kalyani’, ‘18’], [‘Ram’, ‘15’]], with open(‘c:\\pyprg\\ch13\\Pupil.csv’, ‘w’) as CF:, writer = csv.writer(CF) , # CF is the file object, writer.writerows(csvData) # csvData is the List name, CF.close(), When you open the “Pupil.csv” file with a text editor, it will show the content as, follows., Student,, Keyboard, Monitor, Mouse, , Age, 17, 18, 15, , In the above program, csv.writer() method converts all the data in the list “csvData” to, strings and create the content as file like object. The writerows () method writes all the data in, to the new CSV file “Pupil.csv”., Note, The writerow() method writes one row at a time. If you need to write all the data at, once you can use writerows() method., , 13.7.2 Modifying An Existing File, Making some changes in the data of the existing file or adding more data is called, modification .For example the “student.csv” file contains the following data., Roll No, 1, 2, 3, 4, 5, , Name, Harshini,, Adhith,, Dhuruv,, egiste,, Venkat,, , City, Chennai, Mumbai, Bengaluru, Tiruchy, Madurai, , The following program modify the “student.csv” file by modifying the value of an, existing row in student.csv, , 255, , Chapter 13.indd 255, , Python and CSV files, , 20-02-2019 15:33:08
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import csv, row = [‘3’, ‘Meena’,’Bangalore’], with open(‘student.csv’, ‘r’) as readFile:, reader = csv.reader(readFile), lines = list(reader) , # list()- to store each row of data as a list, lines[3] = row, with open(‘student.csv’, ‘w’) as writeFile:, # returns the writer object which converts the user data with delimiter, writer = csv.writer(writeFile), #writerows()method writes multiple rows to a csv file, writer.writerows(lines), readFile.close(), writeFile.close(), When we open the student.csv file with text editor, then it will show:, Roll No, , Name, , City, , 1, , Harshini,, , Chennai, , 2, , Adhith,, , Mumbai, , 3, , Dhuruv,, , Bengaluru, , 4, , egiste,, , Tiruchy, , 5, , Venkat,, , Madurai, , In the above program,the third row of “student.csv” is modified and saved. First the, “student.csv” file is read by using csv.reader() function. Then, the list() stores each row of the, file. The statement “lines[3] = row”, changed the third row of the file with the new content in, “row”. The file object writer using writerows (lines) writes the values of the list to “student.csv”, file., , (i) ADDING NEW ROW, Sometimes, you may need to add new rows in the existing CSVfile. Adding a new row, at the end of the file is called appending a row., The following program add a new row to the existing “student.csv” file., , XII Std Computer Science, , Chapter 13.indd 256, , 256, 256, , 20-02-2019 15:33:08
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import csv, row = [‘6’, ‘Sajini ‘, ‘Madurai’], with open(‘student.csv’, ‘a’) as CF: , # append mode to add data at the end, writer = csv.writer(CF), writer.writerow(row), # writerow() method write a single row of data in file, CF.close(), When “student.csv” file is opened with a text editor, it displays as follows, Roll No, , Name, , City, , 1, , Harshini,, , Chennai, , 2, , Adhith,, , Mumbai, , 3, , Meena, , Bengaluru, , 4, , egiste,, , Tiruchy, , 5, , Venkat,, , Madurai, , 6, , Sajini ,, , Madurai, , In the above program, a new row is appended into “student.csv”. For this, purpose only, the CSV file is opened in ‘a’ append mode. Append mode write the value of row after the last, line of the “student.csv file.”, The ‘w’ write mode creates a new file. If the file is already existing ‘w’ mode, over writs it. Where as ‘a’ append mode add the data at the end of the file if the file, already exists otherwise creates a new one., , Note, writerow() takes 1-dimensional data (one row), and writerows takes 2-dimensional, data (multiple rows) to write in a file., , 13.7.3 CSV Files With Quotes, You can write the csv file with quotes, by registering new dialects using, csv.register_dialect() class of csv module. The following program explains this., , 257, , Chapter 13.indd 257, , Python and CSV files, , 20-02-2019 15:33:08
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import csv, info = [[‘SNO’, ‘Person’, ‘DOB’],, [‘1’, ‘Madhu’, ‘18/12/2001’],, [‘2’, ‘Sowmya’,’19/2/1998’],, [‘3’, ‘Sangeetha’,’20/3/1999’],, [‘4’, ‘Eshwar’, ‘21/4/2000’],, [‘5’, ‘Anand’, ‘22/5/2001’]], csv.register_dialect(‘myDialect’,quoting=csv.QUOTE_ALL), with open(‘c:\\pyprg\\ch13\\person.csv’, ‘w’) as f:, writer = csv.writer(f, dialect=’myDialect’), for row in info:, writer.writerow(row), f.close(), When you open “person.csv” file, we get following output :, “SNO”,”Person”,”DOB” ”1”,”Madhu”,”18/12/2001”, ”2”,”Sowmya”,”19/2/1998” ”3”,”Sangeetha”,”20/3/1999”, ”4”,”Eshwar”,”21/4/2000”, “5”,”Anand”,”22/5/2001”, In above program, a dialect named myDialect is registered(declared). Quoting=csv., QUOTE_ALL allows to write the double quote on all the values., , 13.7.4 CSV Files With Custom Delimiters, A delimiter is a string used to separate fields. The default value is comma(,)., You can have custom delimiter in CSV files by registering a new dialect with the help of, csv.register_dialect().This example Program is written using the custom delimiter pipe(|), import csv, info = [[‘SNO’, ‘Person’, ‘DOB’],, [‘1’, ‘Madhu’, ‘18/12/2001’],, [‘2’, ‘Sowmya’,’19/2/1998’],, [‘3’, ‘Sangeetha’,’20/3/1999’],, [‘4’, ‘Eshwar’, ‘21/4/2000’],, [‘5’, ‘Anand’, ‘22/5/2001’]], csv.register_dialect(‘myDialect’,delimiter = ‘|’), with open(‘c:\pyprg\ch13\dob.csv’, ‘w’) as f:, writer = csv.writer(f, dialect=’myDialect’), for row in info:, writer.writerow(row), f.close(), XII Std Computer Science, , Chapter 13.indd 258, , 258, 258, , 20-02-2019 15:33:08
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When we open “dob.csv” file, we get the following output:, Roll No, , Name, , City, , 1, , Madhu, , 18/12/2001, , 2, , Sowmya, , 19/2/1998, , 3, , Sangeetha, , 20/3/1999, , 4, , Eshwar, , 21/4/2000, , 5, , Anand,, , 22/5/2001, , In the above program, a dialect with delimiter as pipe(|)is registered. Then the list “info”, is written into the CSV file “dob.csv”., Note, The dialect parameter skipinitialspace when it is True, whitespace immediately following, the delimiter is ignored. The default is False., , 13.7.5 CSV File With A Line Terminator, A Line Terminator is a string used to terminate lines produced by writer. The default, value is \r or \n. We can write csv file with a line terminator in Python by registering new, dialects using csv.register_dialect() class of csv module. For Example, import csv, Data = [[‘Fruit’, ‘Quantity’], [‘Apple’, ‘5’], [‘Banana’, ‘7’], [‘Mango’, ‘8’]], csv.register_dialect(‘myDialect’, delimiter = ‘|’, lineterminator = ‘\n’), with open(‘c:\\pyprg\\ch13\\line.csv’, ‘w’) as f:, writer = csv.writer(f, dialect=’myDialect’), writer.writerows(Data), f.close(), When we open the line.csv file, we get following output with spacing between lines:, Fruit, Apple, Banana, Mango, , Quantity, 5, 7, 8, , In the above code, the new dialect “myDialect uses the delimiter=’|’ where a | (pipe) is, considered as column separator. The line terminator=’\r\n\r\n’ separates each row and display, the data after every two lines., , 259, , Chapter 13.indd 259, , Python and CSV files, , 20-02-2019 15:33:08
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Note, Python’s CSV module only accepts \r\n, \n or \r as line terminator., , 13.7.6 CSV File with quote characters, You can write the CSV file with custom quote characters, by registering new dialects, using csv.register_dialect() class of csv module., import csv, csvData = [[‘SNO’,’Items’], [‘1’,’Pen’], [‘2’,’Book’], [‘3’,’Pencil’]], csv.register_dialect(‘myDialect’,delimiter = ‘|’,quotechar = ‘”’,, quoting=csv.QUOTE_ALL), with open(‘c:\\pyprg\\ch13\\quote.csv’, ‘w’) as csvFile:, writer = csv.writer(csvFile, dialect=’myDialect’), writer.writerows(csvData), print(“writing completed”), csvFile.close(), When you open the “quote.csv” file in notepad, we get following output:, Sl.No, 1, 2, 3, , ”Items”, ”Pen”, ”Book”, ”Pencil”, , In the above program, myDialect uses pipe (|) as delimiter and quotechar as doublequote, ‘”’ to write inside the file., , 13.7.7 Writing CSV File Into A Dictionary, Using DictWriter() class of csv module, we can write a csv file into a dictionary. It, creates an object which maps data into a dictionary. The keys are given by the fieldnames, parameter. The following program helps to write the dictionary in to file., import csv, data = [{‘MOUNTAIN’ : ‘Everest’, ‘HEIGHT’: ‘8848’},, {‘MOUNTAIN’ : ‘Anamudi ‘, ‘HEIGHT’: ‘2695’},, {‘MOUNTAIN’ : ‘Kanchenjunga’, ‘HEIGHT’: ‘8586’}], with open(‘c:\\pyprg\\ch13\\peak.csv’, ‘w’) as CF:, fields = [‘MOUNTAIN’, ‘HEIGHT’], w = csv.DictWriter(CF, fieldnames=fields), w.writeheader(), w.writerows(data), print(“writing completed”), CF.close(), XII Std Computer Science, , Chapter 13.indd 260, , 260, 260, , 20-02-2019 15:33:08
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When you open the “peak.csv” file in notepad, you get the following output:, MOUNTAIN,, , HEIGHT, , Everest,, , 8848, , Anamudi ,, , 2695, , Kanchenjunga,, , 8586, , In the above program, use fieldnames as headings of each column in csv file. Then, use, a DictWriter() to write dictionary data into “peak.csv” file., , 13.7.7.1 Writing Dictionary Into CSV File With Custom Dialects, import csv, csv.register_dialect(‘myDialect’, delimiter = ‘|’, quoting=csv.QUOTE_ALL), with open(‘c:\\pyprg\\ch13\\grade.csv’, ‘w’) as csvfile:, fieldnames = [‘Name’, ‘Grade’], writer = csv.DictWriter(csvfile, fieldnames=fieldnames, dialect=”myDialect”), writer.writeheader(), writer.writerows([{‘Grade’: ‘B’, ‘Name’: ‘Anu’},, , {‘Grade’: ‘A’, ‘Name’: ‘Beena’},, , {‘Grade’: ‘C’, ‘Name’: ‘Tarun’}]), print(“writing completed”), When we open grade.csv file, it will contain following output:, “Name”, , ”Grade”, , ”Anu”, , ”B”, , ”Beena”, , ”A”, , “Tarun”, , ”C”, , In the above program, a custom dialect called myDialect with pipe (|) as delimiter uses, the fieldnames as headings of each column to write in a csv file. Finally, we use a DictWriter(), to write dictionary data into “grade.csv” file., , 13.7.8 Getting Data At Runtime And Writing It In a CSV File, You can even accept the data through keyboard and write in to a CSV file. For example, the following program accept data from the user through key board and stores it in the file, called “dynamicfile.csv”. It also displays the content of the file., , 261, , Chapter 13.indd 261, , Python and CSV files, , 20-02-2019 15:33:08
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import csv, with open(‘c:\\pyprg\\ch13\\dynamicfile.csv’, ‘w’) as f:, w = csv.writer(f), ans=’y’, while (ans==’y’):, name = input(“Name?: “), date = input(“Date of birth: “), place = input(“Place: “), w.writerow([name, date, place]), ans=input(“Do you want to enter more y/n?: “), F=open(‘c:\\pyprg\\ch13\\dynamicfile.csv’,’r’), reader = csv.reader(F), for row in reader:, print(row), F.close(), , XII Std Computer Science, , Chapter 13.indd 262, , H8, , 1, 2, 3, 4, 5, 6, , >, , OUTPUT, Name?: Nivethitha, Date of birth: 12/12/2001, Place: Chennai, Do you want to enter more y/n?: y, Name?: Leena, Date of birth: 15/10/2001, Place: Nagercoil, Do you want to enter more y/n?: y, Name?: Padma, Date of birth: 18/08/2001, Place: Kumbakonam, Do you want to enter more y/n?: n, [‘Nivethitha’, ‘12/12/2001’, ‘Chennai’], [], [‘Leena’, ‘15/10/2001’, ‘Nagercoil’], [], [‘Padma’, ‘18/08/2001’, ‘Kumbakonam’], , A, B, Nivethitha 12/12/2001, , fx, , C, Chennai, , Leena, , 15/10/2001, , Nagercoil, , Padma, , 18/08/2001, , Kumbakonam, , 262, 262, , 20-02-2019 15:33:08
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Points to remember:, • A CSV file is a human readable text file where each line has a number of fields, separated, by commas or some other delimiter, • Excel is a binary file whereas CSV format is a plain text format, • The two ways to read a CSV file are using csv.reader() function and using DictReader, class., • The default mode of csv file in reading and writing is text mode, • Binary mode can be be used when dealing with non-text files like image or exe files., • Python has a garbage collector to clean up unreferenced objects, • close() method will free up the resources that were tied with the file, • By default CSV files should open automatically in Excel, • The CSV library contains objects and other code to read, write, and process data from, and to CSV files., • “skipinitialspace” is used for removing whitespaces after the delimiter, • To sort by more than one column operator.itemgetter() can be used, • DictReader() class of csv module creates an object which maps data to a dictionary, • CSV file having custom delimiter is read with the help of csv.register_dialect()., • To sort by more than one column itemgetter() with multiple indices is used., • csv.reader and csv.writer work with list/tuple, while csv.DictReader and csv.DictWriter, work with dictionary ., • csv.DictReader and csv.DictWriter take additional argument fieldnames that are used, as dictionary keys., • The function dict() is used to print the data in dictionary format without order., • The csv.writer() method returns a writer object which converts the user’s data into, delimited strings., • The writerow() method writes one row at a time. Writerows() method is used to write, all the data at once, • Adding a new row at the end of the file is called appending a row., , 263, , Chapter 13.indd 263, , Python and CSV files, , 20-02-2019 15:33:08
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Hands on Experience, 1., , Write a Python program to read the following Namelist.csv file and sort the data in, alphabetically order of names in a list and display the output, 1, , A, SNO, , 2, 3, 4, 5, 6, , 2., , B, , NAME, 1, 2, 3, 4, 5, , NIVETHITHA, ADHITH, LAVANYA, VIDHYA, BINDHU, , C, OCCUPATION, ENGINEER, DOCTOR, SINGER, TEACHER, LECTURER, , Write a Python program to accept the name and five subjects mark of 5 students .Find, the total and store all the details of the students in a CSV file, , Evaluation, Part - I, , Choose the best answer, 1., , 2., , (1 Marks), , A CSV file is also known as a …., (A) Flat File, , (B) 3D File, , (C) String File, , (D) Random File, , The expansion of CRLF is, (A) Control Return and Line Feed, (B) Carriage Return and Form Feed, (C) Control Router and Line Feed, (D) Carriage Return and Line Feed, , 3., , Which of the following module is provided by Python to do several operations on the, CSV files?, (A) py, , (B) xls, , (C) csv, , (D) os, , XII Std Computer Science, , Chapter 13.indd 264, , 264, 264, , 20-02-2019 15:33:08
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4., , 5., , 6., , 7., , Which of the following mode is used when dealing with non-text files like image or exe files?, (A) Text mode, , (B) Binary mode, , (C) xls mode, , (D) csv mode, , The command used to skip a row in a CSV file is, (A) next(), , (B) skip(), , (C) omit(), , (D) bounce(), , Which of the following is a string used to terminate lines produced by writer()method of, csv module?, (A) Line Terminator, , (B) Enter key, , (C) Form feed, , (D) Data Terminator, , What is the output of the following program? import csv, d=csv.reader(open('c:\PYPRG\ch13\city.csv')), next(d), for row in d:, print(row), if the file called “city.csv” contain the following details, chennai,mylapore, mumbai,andheri, A) chennai,mylapore, , (B) mumbai,andheri, , (C) chennai, , (D) chennai,mylapore, , mumba, 8., , 9., , mumbai,andheri, , Which of the following creates an object which maps data to a dictionary?, (A) listreader(), , (B) reader(), , (C) tuplereader(), , (D) DicReader (), , Making some changes in the data of the existing file or adding more data is called, (A)Editing, , (B) Appending, , (C)Modification, , (D) Alteration, , 10. What will be written inside the file test.csv using the following program, import csv, D = [['Exam'],['Quarterly'],['Halfyearly']], csv.register_dialect('M',lineterminator = '\n'), 265, , Chapter 13.indd 265, , Python and CSV files, , 20-02-2019 15:33:08
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with open('c:\pyprg\ch13\line2.csv', 'w') as f:, wr = csv.writer(f,dialect='M'), wr.writerows(D), f.close(), (A) Exam Quarterly Halfyearly, , (B) Exam Quarterly Halfyearly, , (C) E, Q, H, , (D) Exam,, Quarterly,, Halfyearly, Part - II, , Answer the following questions, 1., 2., 3., 4., 5., , (2 Marks), , What is CSV File?, Mention the two ways to read a CSV file using Python., Mention the default modes of the File., What is use of next() function?, How will you sort more than one column from a csv file?Give an example statement., Part - III, , Answer the following questions, 1., 2., 3., 4., 5., , (3 Marks), , Write a note on open() function of python. What is the difference between the two, methods?, Write a Python program to modify an existing file., Write a Python program to read a CSV file with default delimiter comma (,)., What is the difference between the write mode and append mode., What is the difference between reader() and DictReader() function?, Part - IV, , Answer the following questions, 1., 2., 3., 4., 5., , (5 Marks), , Differentiate Excel file and CSV file., Tabulate the different mode with its meaning., Write the different methods to read a File in Python., Write a Python program to write a CSV File with custom quotes., Write the rules to be followed to format the data in a CSV file., , REFERENCES, 1. Python for Data Analysis, Data Wrangling with Pandas, NumPy, and IPython By, William McKinney, 2. CSV File Reading and Writing - Python 3.7.0 documentation, 3. https://docs.python.org, XII Std Computer Science, , Chapter 13.indd 266, , 266, 266, , 20-02-2019 15:33:08
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Unit, , V, , CHAPTER 14, IMPORTING C++ PROGRAMS IN PYTHON, , Learning Objectives, After the completion of this chapter, the student will be able to, • Understand what is wrapping., • Able to import C++ functions and classes in to Python programs., • Create environment to work with both languages., • Execute and debug Python programs., , 14.1 Introduction, Python and C++ are general-purpose programming language. However, Python is, quite different from C++., S.NO, , PYTHON, , C++, , 1, , Python is typically an "interpreted", language, , C++ is typically a "compiled", language, , 2, , Python is a dynamic-typed, language, , C++ is compiled statically typed, language, , 3, , Data type is not required while, declaring variable, , Data type is required while, declaring variable, , 4, , It can act both as scripting and general, purpose language, , It is a general purpose language, , Yet these two languages complement one another perfectly. Python is mostly used as a, scripting or "glue", language. That is, the top level program mostly calls routines written in C, or C++. This is useful when the logic can be written in terms of existing code (For example a, program written in C++) but can be called and manipulated through Python program., , Chapter 14.indd 267, , 20-02-2019 15:36:06
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14.2 Scripting Language, A scripting language is a programming language designed for integrating and, communicating with other programming languages. Some of the most widely used scripting, languages are JavaScript, VBScript, PHP, Perl, Python, Ruby, ASP and Tcl. Since a scripting, language is normally used in conjunction with another programming language, they are often, found alongside HTML, Java or C++., 14.2.1 Difference between Scripting and Programming Languages, Scripting Language and Programming Language looks like the following picture., , 9, 6, Basically, all scripting languages are programming languages. The theoretical difference, between the two is that scripting languages do not require the compilation step and are rather, interpreted. For example, normally, a C++ program needs to be compiled before running, whereas, a scripting language like JavaScript or Python need not be compiled. A scripting, language requires an interpreter while a programming language requires a compiler. A given, language can be called as a scripting or programming language depending on the environment, they are put to use., , 14.3, , Applications of Scripting Languages, , 1. To automate certain tasks in a program, 2. Extracting information from a data set, 3. Less code intensive as compared to traditional programming language, 4. can bring new functions to applications and glue complex systems together, Python is actually an interpreted, high-level, general-purpose programming language, that can be used on any modern computer operating system. It can be used for processing text,, numbers, images, scientific data and just about anything else you might save on a computer., Now a days, large applications are written almost exclusively in Python., , XII Std Computer Science, , Chapter 14.indd 268, , 268, , 20-02-2019 15:36:07
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14.4 Features of Python over C++, • Python uses Automatic Garbage Collection whereas C++ does not., • C++ is a statically typed language, while Python is a dynamically typed language., • Python runs through an interpreter, while C++ is pre-compiled., • Python code tends to be 5 to 10 times shorter than that written in C++., • In Python, there is no need to declare types explicitly where as it should be done in C++, • In Python, a function may accept an argument of any type, and return multiple values, without any kind of declaration beforehand. Whereas in C++ return statement can return, only one value., Note, Python deletes unwanted objects (built-in types or class instances) automatically, to free the memory space. The process by which Python periodically frees and reclaims, blocks of memory that no longer are in use is called Garbage Collection., , 14.5 Importing C++ Files in Pythona, Importing C++ program in a Python program is called wrapping up of C++ in Python., Wrapping or creating Python interfaces for C++ programs are done in many ways. The, commonly used interfaces are, • Python-C-API (API-Application Programming Interface for interfacing with C, programs), • Ctypes (for interfacing with c programs), • SWIG (Simplified Wrapper Interface Generator- Both C and C++), • Cython (Cython is both a Python-like language for writing, C-extensions), • Boost. Python (a framework for interfacing Python and C++), • MinGW (Minimalist GNU for Windows), 14.5.1 MinGW Interface, MinGW refers to a set of runtime header files, used in compiling and linking the code, of C, C++ and FORTRAN to be run on Windows Operating System., MinGw-W64 (version of MinGW) is the best compiler for C++ on Windows. To compile, and execute the C++ program, you need ‘g++’ for Windows. MinGW allows to compile and, execute C++ program dynamically through Python program using g++., 269, , Chapter 14.indd 269, , Importing C++ programs in Python, , 20-02-2019 15:36:07
Page 276 : Python program that contains the C++ coding can be executed only through, minGW-w64 project’ run terminal. The run terminal open the command-line window through, which Python program should be executed., g++ is a program that calls GCC (GNU C Compiler) and automatically links the, required C++ library files to the object code., Refer installation of MinGW in Annexure -3, , 14.5.2 Executing C++ Program through Python, 1., , Double click the run terminal of MinGW, , 2., , Go to the folder where the Python software is located (Python.exe) is located. In this, example “Python folder” is located in, For example here “Python” is located in, C:\Program Files\OpenOffiice 4\Python., , The syntax to change from c:\> to the folder where Python is located is, cd <absolute path>, where “cd” command refers to change directory and absolute path refers to the complete, path where Python is installed., c:\>cd c:\ program files \ openoffice 4 \ program, c:\ Program Files\OpenOffice 4\program>python, Python 2. 7. 6 <default. Dec 11 2017 16:54:32> [Msc v.1500 32 bit <Intel>] On win 32, Type "help", "copyright", "credits" or "license" for more information, >>>, , Figure 14.1, In this Example to go to the folder where Python is located we should type the following, command “cd C:\Program Files\OpenOffiice 4\Program”. See that highlighted area in the, above window., Consider the Example pycpp.py is a Python program which will read the C++program, Pali.cpp. The “Pali.cpp” program accepts a number and display whether it is a “Palindrome or, Not”. For example the entered input number is 232 the output displayed will be “Palindrome”., The C++ program Pali is typed in notepad and saved as pali.cpp. Same way the Python, program pycpp.py code is also typed in notepad and saved as pycpp.py., XII Std Computer Science, , Chapter 14.indd 270, , 270, , 20-02-2019 15:36:07
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3., , To execute our program double click the run terminal change the path to the Python, folder location. The syntax to execute the Python program is, Python <filename.py> -i <C++ filename without cpp extension>, , Where,, Python, , keyword to execute the Python program from commandline, , filename.py, , Name of the Python program to executed, , -i, , input mode, , C++ filename without, cpp extension, , name of C++ file to be compiled and executed, , For example type Python pycpp.py –i pali in the command prompt and press enter key., If the compilation is successful you will get the desired output. Otherwise the error will be, displayed., Note, In the execution command, the input file doesn’t require its extension. For, example, it is enough to mention just the name “pali” instead of “pali.cpp”., Now let us will see the execution through our example pycpp.py and pali.cpp. These, two programs are stored in the folder c:\pyprg. If the programs are not located in same folder, where the Python exe file is there then the complete path must be specified for the files during, execution. The output is displayed below, C:\Program Files\migw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0>echo off, Microsoft windows [Version 6.1.7601], copy right <c> 2009 Microsoft Corporation. All rights reserved., C:\>cd program files\openoffice 4 program, C:\Program Files\openoffice 4\program> Python c:\pyprg\pycpp.py-i c:\pyprg\pali, compailing c:\pyprg\pali.cpp, Running c:\pyprg\pali.exe, ----------------------Enter apositive number:232, The reverse of the number is:232, The number is a palindrome, C:\Program jFiles\Openoffice 4\program>Python c:\pyprg\pycpp.py -i c:\pyprg\pali, Compiling c:\pyprg\pali.cpp, Running c:\pyprg\pali.exe, ----------------------Enter a positive number:234, The reverse of the number is:432, The number is not a palindrome, C:\Program Files\Openoffice 4\program>_, , Fig 14.2, , 271, , Chapter 14.indd 271, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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Note, To clear the screen in command window use cls command., Now let us will see how to write the Python program for compiling C++ code., , 14.6 Python Program to import C++, Python contains many modules. For a problem Python allow programmers to have the, flexibility in using different module as per their convenience. The Python program what we, have written contains a few new commands which we have not come across in basic Python, program. Since our program is an integration of two different languages, we have to import the, modules like os, sys and getopt., , 14.6.1 MODULE, Modular programming is a software design technique to split your code into separate, parts. These parts are called modules. The focus for this separation should have modules with no, or just few dependencies upon other modules. In other words: Minimization of dependencies, is the goal., But how do we create modules in Python? Modules refer to a file containing Python, statements and definitions. A file containing Python code, for e.g. factorial.py, is called a module, and its module name would be factorial. We use modules to break down large programs into, small manageable and organized files. Furthermore, modules provide reusability of code., We can define our most used functions in a module and import it, instead of copying their, definitions into different programs., , Example:, def fact(n):, f=1, if n == 0:, return 0, elif n == 1:, return 1, else:, , for i in range(1, n+1):, f= f*i, print (f), Output:, >>>fact (5), 120, The above example is named as factorial.py, XII Std Computer Science, , Chapter 14.indd 272, , 272, , 20-02-2019 15:36:07
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14.6.2 How to import modules in Python?, We can import the definitions inside a module to another module. We use the import, keyword to do this. To import our previously defined module factorial we type the following, in the Python prompt., >>> import factorial, Using the module name we can access the functions defined inside the module. The, dot (.) operator is used to access the functions. The syntax for accessing the functions from, the module is, <module name> . <function name>, For example:, >>> factorial.fact(5), 120, factorial . fact (5), Function call, Dot operator, Module name, Python has number of standard (built in) modules. Standard modules can be imported, the same way as we import our user-defined modules. We are now going to see the Standard, modules which are required for our program to run C++ code., , (i) Python’s sys module, This module provides access to some variables used by the interpreter and to functions, that interact strongly with the interpreter., , sys.argv, sys.argv is the list of command-line arguments passed to the Python program. argv, contains all the items that come along via the command-line input, it's basically an array, holding the command-line arguments of the program., To use sys.argv, you will first have to import sys. The first argument, sys.argv[0], is, always the name of the program as it was invoked, and sys.argv[1] is the first argument you, pass to the program (here it is the C++ file). For example, , 273, , Chapter 14.indd 273, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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main(sys.argv[1]), , Accepts the program file (Python program) and the input file (C++, file) as a list(array). argv[0] contains the Python program which, is need not to be passed because by default __main__ contains, source code reference and argv[1] contains the name of the C++, file which is to be processed., , (ii) Python's OS Module, The OS module in Python provides a way of using operating system dependent, functionality., The functions that the OS module allows you to interface with the Windows operating, system where Python is running on., os.system(): Execute the C++ compiling command (a string contains Unix, C command, which also supports C++ command) in the shell (Here it is Command Window). For Example, to compile C++ program g++ compiler should be invoked. To do so the following command, is used., os.system (‘g++’ + <varaiable_name1> ‘-<mode>’ + <variable_name2>, where,, os.system :-, , function system() defined in os module, , g++ :-, , General compiler to compile C++ program under Windows, Operating system., , variable_name1:-, , Name of the C++ file without extension .cpp in string format, , mode :-, , To specify input or output mode. Here it is o prefixed with, hyphen., , variable_name2 :-, , Name of the executable file without extension .exe in string format, , For example the command to compile and execute C++ program is given below, os.system('g++ ' + cpp_file + ' -o ' + exe_file), , g++ compiler compiles the file cpp_file and –o, (output) send to exe_file, , Note, ‘+’ in os.system() indicates that all strings are concatenated as a single string, and send that as a List., , XII Std Computer Science, , Chapter 14.indd 274, , 274, , 20-02-2019 15:36:07
Page 281 : (iii) Python getopt module, The getopt module of Python helps you to parse (split) command-line options and, arguments. This module provides two functions to enable command-line argument parsing., , getopt.getopt method, This method parses command-line options and parameter list. Following is the syntax, for this method −, <opts>,<args>=getopt.getopt(argv, options, [long_options]), Here is the detail of the parameters −, argv −, , This is the argument list of values to be parsed (splited). In our program the complete, command will be passed as a list., , options − This is string of option letters that the Python program recognize as, for input or for, output, with options (like ‘i’ or ‘o’) that followed by a colon (:). Here colon is used, to denote the mode., long_options −This parameter is passed with a list of strings. Argument of Long options, should be followed by an equal sign ('='). In our program the C++ file name, will be passed as string and ‘i’ also will be passed along with to indicate it as, the input file., getopt() method returns value consisting of two elements. Each of these values are, stored separately in two different list (arrays) opts and args .Opts contains list of splitted, strings like mode, path and args contains any string if at all not splitted because of wrong path, or mode. args will be an empty array if there is no error in splitting strings by getopt()., For example The Python code which is going to execute the C++ file p4 in command, line will have the getopt() method like the following one., opts, args = getopt.getopt (argv, "i:",['ifile=']), where opts contains, , [('-i', 'c:\\pyprg\\p4')], , -i :-, , option nothing but mode should be followed by :, , 'c:\\pyprg\\p4', , value nothing but the absolute path of C++ file., , In our examples since the entire command line commands are parsed and no leftover, argument, the second argument args will be empty []. If args is displayed using print(), command it displays the output as []., >>>print(args), [], 275, , Chapter 14.indd 275, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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Note, You can check out the full list of Python standard modules and what they are, for. These files are in the Lib directory inside the location where Python is installed., Some more command for wrapping C++ code, if __name__=='__main__':, main(sys.argv[1:]), __name__ (A Special variable) in Python, Since there is no main() function in Python, when the command to run a Python, program is given to the interpreter, the code that is at level 0 indentation is to be executed., However, before doing that, interpreter will define a few special variables. __name__ is, one such special variable which by default stores the name of the file. If the source file is, executed as the main program, the interpreter sets the __name__ variable to have a value as, “__main__”., __name__ is a built-in variable which evaluates to the name of the current module., Thus it can be used to check whether the current script is being run on its own., For example consider the following, if __name__ == '__main__':, main (sys.argv[1:]), if the command line Python program itself is going to execute first, then __main__, contains the name of that Python program and the Python special variable __name__ also, contain the Python program name. If the condition is true it calls the main which is passed, with C++ file as argument., Note, sys.argv[1:] - get everything after the script name(file name)., Remember “string slicing” you have studied in chapter 8., , 14.7 Python program Executing C++ Program using control statement, Now let us write a Python program to read a C++ coding and execute its result. The, steps for executing the C++ program to check a given number is palindrome or not is given, below, XII Std Computer Science, , Chapter 14.indd 276, , 276, , 20-02-2019 15:36:07
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Type the C++ program to check whether the input number is, Step 1 palindrome or not in notepad and save it as “pali_cpp.cpp”., Step 2, Step 3, Step 4, Step 5, , Type the Python program and save it as pali.py, Click the Run Terminal and open the command window, Go to the folder of Python using cd command., Type the command Python pali.py -i pali_cpp, , Example:- 14.7.1 - Write a C++ program to enter any number and check, whether the number is palindrome or not using while loop., /*. To check whether the number is palindrome or not using while loop.*/, //Now select File->New in Notepad and type the C++ program, #include <iostream>, using namespace std;, int main(), {, int n, num, digit, rev = 0;, cout<< "Enter a positive number: ";, cin>>num;, n = num;, while(num), { digit = num % 10;, rev = (rev * 10) + digit;, num = num / 10; }, cout<< " The reverse of the number is: " << rev <<endl;, if (n == rev), cout<< " The number is a palindrome";, else, cout<< " The number is not a palindrome";, return 0;, }, // Save this file as pali_cpp.cpp, , 277, , Chapter 14.indd 277, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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Output of the above program, C:\Program Files\OpenOffice 4\program>Python c:\pyprg\pali.py -i c:\pyprg\pali_cpp, Compiling c:\pyprg\pali_cpp.cpp, Running c:\pyprg\pali_cpp.exe, -------------------------------------Enter a positive number: 56765, The reverse of the number is: 56765, The number is a palindrome, ----------------------------------------------C:\Program Files\OpenOffice 4\program>Python c:\pyprg\pali.py -i c:\pyprg\pali_cpp, Compiling c:\pyprg\pali_cpp.cpp, Running c:\pyprg\pali_cpp.exe, -------------------------------------Enter a positive number: 56756, The reverse of the number is: 65765, The number is not a palindrome, -----------------------------------------------, , 14.8 How Python is handling the errors in C++, Python not only execute the successful C++ program, it also helps to display even errors, if any in C++ statement during compilation. For example in the following C++ program an, error is there. Let us see what happens when you compile through Python., Example 14.8.1, // C++ program to print the message Hello, //Now select File→New in Notepad and type the C++ program, #include<iostream>, using namespace std;, int main(), {, std::cout<<"hello", return 0;, }, // Save this file as hello.cpp, 279, , Chapter 14.indd 279, , Importing C++ programs in Python, , 20-02-2019 15:36:07
Page 287 : Note, In the above program Python helps to display the error in C++. The error is, displayed along with its line number. The line number starts from python script., , 14.9 Python program Executing C++ Program Containing Arrays, In our previous program to check whether a number is a palindrome number or not, you have used only control structure statements. Now you are going to execute a C++ program, containing array., Example :- 14.9.1, Write a C++ program to print Transpose of a matrix(2 D array).*/, //Now select File->New in Notepad and type the C++ program, #include <iostream>, using namespace std;, int main(), {, int a[3][3], i, j;, for(i=0; i<3; i++), {, for(j=0; j<3; j++), { cout<<"enter the value for array["<<i+1<<"]"<<"["<<j+1<<"] :";, cin>>a[i][j];, }, }, system("cls");, cout<<"\n\nOriginal Array\n";, for(i=0; i<3; i++) {, for(j=0; j<3; j++), cout<<a[i][j]<<' ';, cout<<endl; }, cout<<"\n\n The Transpose of Matrix\n";, for (int i = 0; i < 3; i++), {, for (int j = 0; j < 3; j++), cout<<a[j][i]<<' ';, cout<<endl ;, }, return 0;, }, 281, , Chapter 14.indd 281, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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The Python script (program) in this chapter is mainly used to read the C++ file along, with the type of mode used like ‘i’/’o’. It Parses (splits) each value of the command line and pass, as argument to the List called “opts”. The entire C++ code is referenced for reading by “long, option ifile” along with the mode., The List ‘o’ in “for loop” contains the mode (‘i’) and the variable ‘a’ contains the C++ file, with its complete path (Example [<‘c:\pyprg\cpp_file’>,’ trans_cpp’ ]) The extensions like cpp/, exe are added by the Python script., __name__ variable directs the program to start from the Python script’s “main”, definition. The “main” definition does the Parsing and adding the extensions. The “run”, definition invoke the “g++” compiler and creates the exe file. The system() command of “os”, module executes the exe file and you will get the desired output. The file extensions are added, by the Python script due to which you can even execute the C programs., , 14.10 Python program Executing C++ Program Containing Functions, Now you are going to test the Python script to run a C++ program having functions, and function calls., Example 14.10.1 - Write a C++ program using a user defined function to function, cube of a number, /*Write a C++ program using a user defined function to function cube of a, number.*/, //Now select File→New in Notepad and type the C++ program, #include <iostream>, using namespace std;, // Function declaration, int cube(int num);, int main(), {, int num;, int c;, cout<<"Enter any number: "<<endl;, cin>>num;, c = cube(num);, cout<<"Cube of " <<num<< " is "<<c;, return 0;, }, //Function to find cube of any number, int cube(int num), {, return (num * num * num);, }, 283, , Chapter 14.indd 283, , Importing C++ programs in Python, , 20-02-2019 15:36:07
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14.11 Python program to Illustrate the inheritance of a Class, Now you are going to execute a class program of C++. The class program is of multilevel, inheritance. This also gives output using Python script, Example 14.11.1 - C++ program to implement Multilevel Inheritance, // C++ program to implement Multilevel Inheritance, //Now select File→New in Notepad and type the C++ program, #include <iostream>, using namespace std;, // base class, class Vehicle, {, public:, Vehicle(), {, cout<< "This is a Vehicle" <<endl;, }, };, class threeWheeler: public Vehicle, { public:, threeWheeler(), {, cout<<"Objects with 3 wheels are vehicles"<<endl;, }, };, // sub class derived from two base classes, class Auto: public threeWheeler{, public:, Auto(), {, cout<<"Auto has 3 Wheels"<<endl;, }, };, // main function, int main(), {, //creating object of sub class will invoke the constructor of base classes, Auto obj;, return 0;, }, , 285, , Chapter 14.indd 285, , Importing C++ programs in Python, , 20-02-2019 15:36:08
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// Save this file as inheri_cpp.cpp, //Now select File → New in Notepad and type the Python program, # Save the File as classpy.py, # Python classpy.py -i inheri_cpp command to execute c++ program, import sys, os, getopt, def main (argv):, cpp_file = '', exe_file = '', opts, args = getopt.getopt (argv, "i:",['ifile=']), for o, a in opts:, if o in ("-i", "--ifile"):, cpp_file = a + '.cpp', exe_file = a + '.exe', run (cpp_file, exe_file), def run(cpp_file, exe_file):, print ("Compiling " + cpp_file), os.system ('g++ ' + cpp_file + ' -o ' + exe_file), print ("Running " + exe_file), print ("-------------------"), print, os.system (exe_file), print, if __name__ =='__main__':, main (sys.argv[1:]), Output of the above program, Compiling c:\pyprg\class_file.cpp, Running c:\pyprg\class_file.exe, ------------------This is a Vehicle, Objects with 3 wheels are vehicles, Auto has 3 Wheels, From all these example One can understand the Python script (program) used for, integrating C++ is common. Only the name of the Python script file and the C++ (cpp), file have changed. Remember it is not mandatory to type the C++ coding if one’s computer, contain already the C++ file. In this chapter to show all the types of C++ programs like normal,, function, inheritance program can be executed through python the coding of C++ is explicitly, mentioned. Using this Python script you can even compile and execute C program also. Since, python automates the C++ program file to execute without it’s IDE, Python can be called as a, Scripting Language., , XII Std Computer Science, , Chapter 14.indd 286, , 286, , 20-02-2019 15:36:08
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Points to remember:, • C++ is a compiler based language while Python is an interpreter based language., • C++is compiled statically whereas Python is interpreted dynamically, • A static typed language like C++ requires the programmer to explicitly tell the, computer what “data type” each data value is going to use., • A dynamic typed language like Python, doesn’t require the data type to be given, explicitly for the data. Python manipulate the variable based on the type of value., • A scripting language is a programming language designed for integrating and, communicating with other programming languages, • MinGW refers to a set of runtime header files, used in compiling and linking the code, of C, C++ and FORTRAN to be run on Windows Operating System, • The dot (.) operator is used to access the functions of a imported module, • sys module provides access to some variables used by the interpreter and to functions, that interact with the interpreter, • OS module in Python provides a way of using operating system dependent functionality, • The getopt module of Python helps you to parse (split) command-line options and, arguments, , Hands on Experience, 1., , Write a C++ program to create a class called Student with the following details, Protected member, Rno integer, Public members, void Readno(int); to accept roll number and assign to Rno, void Writeno(); To display Rno., The class Test is derived Publically from the Student class contains the following details, Protected member, Mark1 float, Mark2 float, Public members, void Readmark(float, float); To accept mark1 and mark2, void Writemark(); To display the marks, Create a class called Sports with the following detail, Protected members, 287, , Chapter 14.indd 287, , Importing C++ programs in Python, , 20-02-2019 15:36:08
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score integer, Public members, void Readscore(int); To accept the score, void Writescore(); To display the score, The class Result is derived Publically from Test and Sports class contains the following, details, Private member, Total float, Public member, void display() assign the sum of mark1, mark2, score in total., invokeWriteno(), Writemark() and Writescore(). Display the total also., Save the C++ program in a file called hybrid. Write a python program to execute the, hybrid.cpp, 2., , Write a C++ program to print boundary elements of a matrix and name the file as Border., cpp. Write a python program to execute the Border.cpp, , Evaluation, Part - I, , Choose the best answer, , (1 Marks), , 1. Which of the following is not a scripting language?, (A) JavaScript, , (B) PHP, , (C) Perl, , (D) HTML, , 2. Importing C++ program in a Python program is called, (A) wrapping, , (B) Downloading, , (C) Interconnecting, , (D) Parsing, , 3. The expansion of API is, (A) Application Programming Interpreter, (B) Application Programming Interface, (C) Application Performing Interface, (D) Application Programming Interlink, 4. A framework for interfacing Python and C++ is, , XII Std Computer Science, , Chapter 14.indd 288, , 288, , 20-02-2019 15:36:08
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(A) Ctypes, , (B) SWIG, , (C) Cython, , (D) Boost, , 5. Which of the following is a software design technique to split your code into separate, parts?, (A) Object oriented Programming, (B) Modular programming, (C) Low Level Programming, (D) Procedure oriented Programming, 6. The module which allows you to interface with the Windows operating system is, (A) OS module, , (B) sys module, , (c) csv module, , (d) getopt module, , 7. getopt() will return an empty array if there is no error in splitting strings to, (A) argv variable, , (B) opt variable, , (c)args variable, , (d) ifile variable, , 8. Identify the function call statement in the following snippet., if __name__ =='__main__':, main(sys.argv[1:]), (A) main(sys.argv[1:]), , (B) __name__ (C) __main__ , , (D) argv, , 9. Which of the following can be used for processing text, numbers, images, and scientific, data?, (A) HTML, , (B) C, , (C) C++, , (D) PYTHON, , 10. What does __name__ contains ?, (A) c++ filename, , (B) main() name, , (C) python filename, , (D) os module name, Part - II, , Answer the following questions, 1., , (2 Marks), , What is the theoretical difference between Scripting language and other programming, language?, , 2., , Differentiate compiler and interpreter., , 3., , Write the expansion of, , 4., , What is the use of modules?, , 5., , What is the use of cd command. Give an example., , (i) SWIG , , 289, , Chapter 14.indd 289, , (ii) MinGW, , Importing C++ programs in Python, , 20-02-2019 15:36:08
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Part - III, , Answer the following questions, , (3 Marks), , 1., , Differentiate PYTHON and C++, , 2., , What are the applications of scripting language?, , 3., , What is MinGW? What is its use?, , 4., , Identify the module ,operator, definition name for the following, welcome.display(), , 5., , What is sys.argv? What does it contain?, Part - IV, , Answer the following questions, , (5 Marks), , 1, , Write any 5 features of Python., , 2., , Explain each word of the following command., Python, , <filename.py> -<i> <C++ filename without cpp extension>, , 3., , What is the purpose of sys,os,getopt module in Python.Explain, , 4., , Write the syntax for getopt() and explain its arguments and return values, , 5., , Write a Python program to execute the following c++ coding, #include <iostream>, using namespace std;, int main(), { cout<<“WELCOME”;, return(0);, }, The above C++ program is saved in a file welcome.cpp, , REFERENCES, 1. Learn Python The Hard Way by Zed Shaw, 2. Python Programming Advanced by Adam Stuart or Powerful Python by Aaron Maxwell, 3. https://docs.python.org, , XII Std Computer Science, , Chapter 14.indd 290, , 290, , 20-02-2019 15:36:08
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Unit, , V, , CHAPTER 15, DATA MANIPULATION THROUGH SQL, , Learning Objectives, After the completion of this chapter, the student will be able to write Python script to, • Create a table and to add new rows in the database., • Update and Delete record in a table., • Query the table., • Write the Query in a CSV file., , 15.1 Introduction, A database is an organized collection of data. The term "database" can both refer to the, data themselves or to the database management system. The Database management system is, a software application for the interaction between users and the databases. Users don't have, to be human users. They can be other programs and applications as well. We will learn how, Python program can interact as a user of an SQL database., , 15.2 SQLite, SQLite is a simple relational database system, which saves its data in regular data files, or even in the internal memory of the computer. It is designed to be embedded in applications,, instead of using a separate database server program such as MySQLor Oracle. SQLite is fast,, rigorously tested, and flexible, making it easier to work. Python has a native library for SQLite., To use SQLite,, Step 1, , import sqlite3, , Step 2 create a connection using connect () method and pass the name of the database File, Step 3, , Set the cursor object cursor = connection. cursor (), , • Connecting to a database in step2 means passing the name of the database to be accessed., If the database already exists the connection will open the same. Otherwise, Python will, open a new database file with the specified name., 291, , Chapter 15.indd 291, , 20-02-2019 15:40:09
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• Cursor in step 3: is a control structure used to traverse and fetch the records of the, database., • Cursor has a major role in working with Python. All the commands will be executed, using cursor object only., To create a table in the database, create an object and write the SQL command in it., Example:- sql_comm = "SQL statement", For executing the command use the cursor method and pass the required sql command, as a parameter. Many number of commands can be stored in the sql_comm and can be executed, one after other. Any changes made in the values of the record should be saved by the commend, "Commit" before closing the "Table connection"., , 15.3 Creating a Database using SQLite, The following example 15.3 explains how a connection to be made to a database through, Python sqlite3, # Python code to demonstrate table creation and insertions with SQL, # importing module, import sqlite3, # connecting to the database, connection = sqlite3.connect ("Academy.db"), # cursor, cursor = connection.cursor(), In the above example a database with the name "Academy" would be created. It's, similar to the sql command "CREATE DATABASE Academy;" to SQL server."sqlite3.connect, ('Academy.db')" is again used in some program, "connect" command just opens the already, created database., 15.3.1 Creating a Table, After having created an empty database, you will most probably add one or more tables, to this database. The SQL syntax for creating a table "Student" in the database "Academy" looks, like as follows :, CREATE TABLE Student (, RollnoINTEGER, SnameVARCHAR(20), GradeCHAR(1), gender CHAR(1),, Average float(5.2), birth_date DATE, PRIMARY KEY (Rollno) );, This is the way, somebody might do it on a SQL command shell. Of course, we want to, do this directly from Python. To be capable to send a command to "SQL", or SQLite, we need a, XII Std Computer Science, , Chapter 15.indd 292, , 292, , 20-02-2019 15:40:09
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cursor object. Usually, a cursor in SQL and databases is a control structure to traverse over, the records in a database. So it's used for the fetching of the results., Note, Cursor is used for performing all SQL commands., The cursor object is created by calling the cursor() method of connection. The cursor is, used to traverse the records from the result set. You can define a SQL command with a triple, quoted string in Python. The reason behind the triple quotes is sometime the values in the, table might contain single or double quotes., Example 15.3.1, sql_command = """, CREATE TABLE Student (, Rollno INTEGER PRIMARY KEY ,, Sname VARCHAR(20),, Grade CHAR(1),, gender CHAR(1),, Average DECIMAL(5,2),, birth_date DATE);""", In the above example the Emp_no field as "INTEGER PRIMARY KEY" A column, which is labeled like this will be automatically auto-incremented in SQLite3. To put it in other, words: If a column of a table is declared to be an INTEGER PRIMARY KEY, then whenever, a NULL will be used as an input for this column, the NULL will be automatically converted, into an integer which will one larger than the highest value so far used in that column. If, the table is empty, the value 1 will be used., 15.3.2 Adding Records, To populate (add record) the table "INSERT" command is passed to SQLite. “execute”, method executes the SQL command to perform some action. The following example 15.3.2, is a complete working example. To run the program you will either have to remove the file, Academy. db or uncomment the "DROP TABLE" line in the SQL command:, , 293, , Chapter 15.indd 293, , Data Manipulation through SQL, , 20-02-2019 15:40:09
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Example, import sqlite3, connection = sqlite3.connect ("Academy.db"), cursor = connection.cursor(), # delete, cursor.execute ("""DROP TABLE Student;"""), sql_command = """, CREATE TABLE Student (, Rollno INTEGER PRIMARY KEY , Sname VARCHAR(20), Grade CHAR(1),, gender CHAR(1), Average DECIMAL (5, 2), birth_date DATE);""", cursor.execute(sql_command), sql_command = """INSERT INTO Student (Rollno, Sname, Grade, gender, Average,, birth_date), VALUES (NULL, "Akshay", "B", "M","87.8", "2001-12-12");""" cursor.execute(sql_, command), sql_command = """INSERT INTO Student (Rollno, Sname, Grade, gender, Average,, birth_date), VALUES (NULL, "Aravind", "A", "M","92.50","2000-08-17");""" cursor.execute(sql_, command), # never forget this, if you want the changes to be saved:, connection.commit(), connection.close(), print("STUDENT TABLE CREATED"), OUTPUT, STUDENT TABLE CREATED, Of course, in most cases, you will not literally insert data into a SQL table. You will, rather have a lot of data inside of some Python data type e.g. a dictionary or a list, which has, to be used as the input of the insert statement., The following working example, assumes that you have an already existing database, Academy.db and a table Student. We have a list with data of persons which will be used in the, INSERT statement:, , XII Std Computer Science, , Chapter 15.indd 294, , 294, , 20-02-2019 15:40:09
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Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), student_data = [("BASKAR", "C", "M","75.2","1998-05-17"),, ("SAJINI", "A", "F","95.6","2002-11-01"),, ("VARUN", "B", "M","80.6","2001-03-14"),, ("PRIYA", "A", "F","98.6","2002-01-01"),, ("TARUN", "D", "M","62.3","1999-02-01") ], for p in student_data:, format_str = """INSERT INTO Student (Rollno, Sname, Grade, gender,Average,, birth_date), VALUES (NULL,"{name}", "{gr}", "{gender}","{avg}","{birthdate}");""", sql_command = format_str.format(name=p[0], gr=p[1], gender=p[2],avg=p[3],, birthdate = p[4]), cursor.execute(sql_command), connection.commit(), connection.close(), print("RECORDS ADDED TO STUDENT TABLE "), OUTPUT, RECORDS ADDED TO STUDENT TABLE, , 15.4 SQL Query Using Python, The time has come now to finally query our “Student” table. Fetching the data from, record is as simple as inserting them. The execute method uses the SQL command to get all, the data from the table., 15.4.1 SELECT Query, “Select” is the most commonly used statement in SQL. The SELECT Statement in SQL, is used to retrieve or fetch data from a table in a database. The syntax for using this statement, is “Select * from table_name” and all the table data can be fetched in an object in the form of, list of lists., 295, , Chapter 15.indd 295, , Data Manipulation through SQL, , 20-02-2019 15:40:09
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If you run this program, saved as "sql_Academy_query.py", you would get the following, result, depending on the actual data:, It should be noted that the database file that will be created will be in the same folder as, that of the python file. If we wish to change the path of the file, change the path while opening, the file., Example, #save the file as “sql_Academy_query.py”, # cursor object, crsr = connection.cursor(), # execute the command to fetch all the data from the table Student, crsr.execute("SELECT * FROM Student"), # store all the fetched data in the ans variable, ans= crsr.fetchall(), # loop to print all the data, for i in ans:, print(i), (i) Displaying all records using fetchall(), The fetchall() method is used to fetch all rows from the database table, Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT * FROM student"), print("fetchall:"), result = cursor.fetchall(), for r in result:, print(r), OUTPUT, fetchall:, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), (4, 'SAJINI', 'A', 'F', 95.6, '2002-11-01'), (5, 'VARUN', 'B', 'M', 80.6, '2001-03-14'), (6, 'PRIYA', 'A', 'F', 98.6, '2002-01-01'), (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), XII Std Computer Science, , Chapter 15.indd 296, , 296, , 20-02-2019 15:40:10
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Note, cursor.fetchall() -fetchall () method is to fetch all rows from the database table, cursor.fetchone() - The fetchone () method returns the next row of a query result set or, None in case there is no row left., cursor.fetchmany() method that returns the next number of rows (n) of the result set, (ii) Displaying A record using fetchone(), The fetchone() method returns the next row of a query result set or None in case there, is no row left., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT * FROM student"), print("\nfetch one:"), res = cursor.fetchone(), print(res), OUTPUT, fetch one:, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (iii) Displaying all records using fetchone(), Using while loop and fetchone() method we can display all the records from a table., Example, OUTPUT, , import sqlite3, , connection = sqlite3.connect("Academy.db") fetching all records one by one:, cursor = connection.cursor(), , (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), , cursor.execute("SELECT * FROM student"), , (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), , print("fetching all records one by one:"), , (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), , result = cursor.fetchone(), , (4, 'SAJINI', 'A', 'F', 95.6, '2002-11-01'), , while result is not None:, , (5, 'VARUN', 'B', 'M', 80.6, '2001-03-14'), , print(result), , (6, 'PRIYA', 'A', 'F', 98.6, '2002-01-01'), , result = cursor.fetchone(), , (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), , 297, , Chapter 15.indd 297, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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(iv) Displayingusing fetchmany(), Displaying specified number of records is done by using fetchmany(). This method, returns the next number of rows (n) of the result set., Example : Program to display the content of tuples using fetchmany(), import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT * FROM student"), print("fetching first 3 records:"), result = cursor.fetchmany(3), print(result), OUTPUT, fetching first 3 records:, [(1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), (3,, 'BASKAR', 'C', 'M', 75.2, '1998-05-17')], Example : Program to display the content of tuples in newline without using loops, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT * FROM student"), print("fetching first 3 records:"), result = cursor.fetchmany(3), print(*result,sep="\n"), OUTPUT, fetching first 3 records:, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), Note, symbol is used to print the list of all elements in a single line with space. To print all, elements in new lines or separated by space use sep= "\n" or sep= "," respectively., , XII Std Computer Science, , Chapter 15.indd 298, , 298, , 20-02-2019 15:40:10
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15.4.2 CLAUSES IN SQL, SQL provides various clauses that can be used in the SELECT statements. This clauses, can be called through python script. Almost all clauses will work with SQLite. The following, frequently used clauses are discussed here, • DISTINCT, • WHERE, • GROUP BY, • ORDER BY., • HAVING, (i) SQL DISTINCT CLAUSE, The distinct clause is helpful when there is need of avoiding the duplicate values present, in any specific columns/table. When we use distinct keyword only the unique values are, fetched. In this example we are going to display the different grades scored by students from, “student table”., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT DISTINCT (Grade) FROM student"), result = cursor.fetchall(), print(result), OUTPUT, [('B',), ('A',), ('C',), ('D',)], Without the keyword “distinct” in the above examples 7 records would have been, displayed instead of 4, since in the original table there are actually 7 records and some are with, the duplicate values., (ii) SQL WHERE CLAUSE, The WHERE clause is used to extract only those records that fulfill a specified condition., In this example we are going to display the different grades scored by male students from, “student table”, , 299, , Chapter 15.indd 299, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT DISTINCT (Grade) FROM student where gender='M'"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, ('B',), ('A',), ('C',), ('D',), (iii) SQL Group By Clause, The SELECT statement can be used along with GROUP BY clause. The GROUP BY, clause groups records into summary rows. It returns one records for each group. It is often, used with aggregate functions (COUNT, MAX, MIN, SUM, AVG) to group the result-set by, one or more columns. The following example count the number of male and female from the, student table and display the result., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT gender,count(gender) FROM student Group BY gender"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, ('F', 2), ('M', 5), (iv) SQL ORDER BY Clause, The ORDER BY Clause can be used along with the SELECT statement to sort the data, of specific fields in an ordered way. It is used to sort the result-set in ascending or descending, order. In this example name and Rollno of the students are displayed in alphabetical order of, names, , XII Std Computer Science, , Chapter 15.indd 300, , 300, , 20-02-2019 15:40:10
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Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT Rollno,sname FROM student Order BY sname"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, (1, 'Akshay'), (2, 'Aravind'), (3, 'BASKAR'), (6, 'PRIYA'), (4, 'SAJINI'), (7, 'TARUN'), (5, 'VARUN'), (v) SQL HAVING Clause, Having clause is used to filter data based on the group functions. This is similar to, WHERE condition but can be used only with group functions. Group functions cannot be, used in WHERE Clause but can be used in HAVING clause., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT GENDER,COUNT(GENDER) FROM Student GROUP BY, GENDER HAVING COUNT(GENDER)>3"), result = cursor.fetchall(), co = [i[0] for i in cursor.description], print(co), print(result), OUTPUT, ['gender', 'COUNT(GENDER)'], [('M', 5)], , 15.5 The SQL AND, OR and NOT Operators, The WHERE clause can be combined with AND, OR, and NOT operators. The AND, and OR operators are used to filter records based on more than one condition. In this example, you are going to display the details of students who have scored other than ‘A’ or ‘B’ from the, “student table”, 301, , Chapter 15.indd 301, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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Example for WHERE WITH NOT Operator, Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT * FROM student where grade<>'A' and Grade<>'B'"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), Example for WHERE WITH AND Operator, In this example we are going to display the name, Rollno and Average of students who, have scored an average between 80 to 90% (both limits are inclusive), Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT Rollno,Same,Average, (Average>=80 AND Average<=90)"), result = cursor.fetchall(), print(*result,sep="\n"), , FROM student WHERE, , OUTPUT, (1, 'Akshay', 87.8), (5, 'VARUN', 80.6), Example for WHERE WITH OR Operator, In this example we are going to display the name and Rollno of students who have not, scored an average between 60 to 70%, , XII Std Computer Science, , Chapter 15.indd 302, , 302, , 20-02-2019 15:40:10
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Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT Rollno,sname FROM student WHERE (Average<60, OR Average>70)"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, (1, 'Akshay'), (2, 'Aravind'), (3, 'BASKAR'), (4, 'SAJINI'), (5, 'VARUN'), (6, 'PRIYA'), , 15.6 Querying A Date Column, In this example we are going to display the name and grade of students who have born, in the year 2001, Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT Rollno,sname FROM student, WHERE(Birth_date>='2001-01-01' ANDBirth_date<='2001-12-01')"), result = cursor.fetchall(), print(*result,sep="\n"), OUTPUT, (5, 'VARUN'), , 303, , Chapter 15.indd 303, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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15.7 Aggregate Functions, These functions are used to do operations from the values of the column and a single, value is returned., , 15.7.1 COUNT() function, , • COUNT(), • SUM(), • MIN(), , • AVG(), • MAX(), , The SQL COUNT() function returns the number of rows in a table satisfying the criteria, specified in the WHERE clause. COUNT() returns 0 if there were no matching rows., Example, Example 1 : In this example we are going to count the number of records(rows), import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT COUNT(*) FROM student "), result = cursor.fetchall(), print(result), Output:, [(7,)], EXAMPLE, Example 2 : In this example we are going to count the number of records by, specifying a column, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT COUNT(AVERAGE) FROM student "), result = cursor.fetchall(), print(result), Output:, [(7,)], Note, NULL values are not counted. In case if we had null in one of the records in, student table for example in Average field then the output would be 6., XII Std Computer Science, , Chapter 15.indd 304, , 304, , 20-02-2019 15:40:10
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15.7.2AVG():, The following SQL statement in the python program finds the average mark of all, students., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT AVG(AVERAGE) FROM student "), result = cursor.fetchall(), print(result), OUTPUT, [(84.65714285714286,)], Note, NULL values are ignored., 15.7.3 SUM():, The following SQL statement in the python program finds the sum of all average in the, Average field of “Student table”., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("SELECT SUM(AVERAGE) FROM student "), result = cursor.fetchall(), print(result), OUTPUT, [(592.6,)], , Note, NULL values are ignored., , 305, , Chapter 15.indd 305, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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15.7.4 MAX() AND MIN() FUNCTIONS, The MAX() function returns the largest value of the selected column., The MIN() function returns the smallest value of the selected column., The following example show the highest and least average student’s name., Example, import sqlite3, connection = sqlite3.connect("Organization.db"), cursor = connection.cursor(), print("Displaying the name of the Highest Average"), cursor.execute("SELECT sname,max(AVERAGE) FROM student "), result = cursor.fetchall(), print(result), print("Displaying the name of the Least Average"), cursor.execute("SELECT sname,min(AVERAGE) FROM student "), result = cursor.fetchall(), print(result), OUTPUT, Displaying the name of the Highest Average, [('PRIYA', 98.6)], Displaying the name of the Least Average, [('TARUN', 62.3)], , 15.8 Updating A Record, You can even update a record (tuple) in a table through python script. The following, example change the name “Priya” to “Priyanka” in a record in “student table”, , XII Std Computer Science, , Chapter 15.indd 306, , 306, , 20-02-2019 15:40:10
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Example, # code for update operation, import sqlite3, # database name to be passed as parameter, conn = sqlite3.connect("Academy.db"), # update the student record, conn.execute("UPDATE Student SET sname ='Priyanka' where Rollno='6'"), conn.commit(), print ("Total number of rows updated :", conn.total_changes), cursor = conn.execute("SELECT * FROM Student"), for row in cursor:, print (row), conn.close(), OUTPUT, Total number of rows updated : 1, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), (4, 'SAJINI', 'A', 'F', 95.6, '2002-11-01'), (5, 'VARUN', 'B', 'M', 80.6, '2001-03-14'), (6, 'Priyanka', 'A', 'F', 98.6, '2002-01-01'), (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), , Note, Remember throughout this chapter student table what we have created is taken as example, to explain the SQL queries .Example 15.3.2 -2 contain the student table with records., , 307, , Chapter 15.indd 307, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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15.9 Deletion Operation, Similar to Sql command to delete a record, Python also allows to delete a record. The, following example delete the content of Rollno 2 from "student table", Example, , # code for delete operation, import sqlite3, # database name to be passed as parameter, conn = sqlite3.connect("Academy.db"), # delete student record from database, conn.execute("DELETE from Student where Rollno='2'"), conn.commit(), print("Total number of rows deleted :", conn.total_changes), cursor =conn.execute("SELECT * FROM Student"), for row in cursor:, print(row), conn.close(), OUTPUT, Total number of rows deleted : 1, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), (4, 'SAJINI', 'A', 'F', 95.6, '2002-11-01'), (5, 'VARUN', 'B', 'M', 80.6, '2001-03-14'), (6, 'Priyanka', 'A', 'F', 98.6, '2002-01-01'), (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), , XII Std Computer Science, , Chapter 15.indd 308, , 308, , 20-02-2019 15:40:10
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Data input by User, , 15.10, , In this example we are going to accept data using Python input() command during, runtime and then going to write in the Table called "Person", Example, # code for executing query using input data, import sqlite3, # creates a database in RAM, con =sqlite3.connect("Academy.db"), cur =con.cursor(), cur.execute("DROP Table person"), cur.execute("create table person (name, age, id)"), print("Enter 5 students names:"), who =[input() for i in range(5)], print("Enter their ages respectively:"), age =[int(input()) for i in range(5)], print("Enter their ids respectively:"), p_id =[int(input())for i in range(5)], n =len(who), for i in range(n):, # This is the q-mark style:, cur.execute("insert into person values (?, ?, ?)", (who[i], age[i], p_id[i])), # And this is the named style:, cur.execute("select * from person"), # Fetches all entries from table, print("Displaying All the Records From Person Table"), print (*cur.fetchall(), sep='\n' ), , 309, , Chapter 15.indd 309, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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OUTPUT, Enter 5 students names:, RAM, KEERTHANA, KRISHNA, HARISH, GIRISH, Enter their ages respectively:, 28, 12, 21, 18, 16, Enter their ids respectively:, 1, 2, 3, 4, 5, Displaying All the Records From Person Table, , ('RAM', 28, 1), , ('KEERTHANA', 12, 2), , ('KRISHNA', 21, 3), , ('HARISH', 18, 4), , ('GIRISH', 16, 5), You can even add records to the already existing table like “Student” Using the above, coding with appropriate modification in the Field Name. To do so you should comment the, create table statement, Note, Execute (sql[, parameters]) :- Executes a single SQL statement. The SQL, statement may be parametrized (i. e. placeholders instead of SQL literals). The sqlite3, module supports two kinds of placeholders: question marks? (“qmark style”) and named, placeholders :name (“named style”)., , XII Std Computer Science, , Chapter 15.indd 310, , 310, , 20-02-2019 15:40:10
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15.11 Using Multiple Table for Querying, Python allows to query more than one table by joining them. In the following example, a new table called “Appointments” which contain the details of students Rollno, Duty, Age is, created. The tables “student” and “Appointments” are joined and displayed the result with the, column headings., Example, import sqlite3, connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), cursor.execute("""DROP TABLE Appointment;"""), sql_command = """, CREATE TABLE Appointment(rollnointprimarkey,Dutyvarchar(10),age int)""", cursor.execute(sql_command), sql_command = """INSERT INTO Appointment (Rollno,Duty ,age ), VALUES ("1", "Prefect", "17");""", cursor.execute(sql_command), sql_command = """INSERT INTO Appointment (Rollno, Duty, age), VALUES ("2", "Secretary", "16");""", cursor.execute(sql_command), # never forget this, if you want the changes to be saved:, connection.commit(), cursor.execute("SELECT, student.rollno,student.sname,Appointment., Duty,Appointment.Age FROM student,Appointment where student., rollno=Appointment.rollno"), #print (cursor.description) to display the field names of the table, co = [i[0] for i in cursor.description], print(co), # Field informations can be read from cursor.description., result = cursor.fetchall(), for r in result:, print(r), OUTPUT, ['Rollno', 'Sname', 'Duty', 'age'], (1, 'Akshay', 'Prefect', 17), (2, 'Aravind', 'Secretary', 16), Note, cursor. description contain the details of each column headings .It will be stored, as a tuple and the first one that is 0(zero) index refers to the column name. Using this, command you can display the table’s Field names., 311, , Chapter 15.indd 311, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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15.12 Integrating Query With Csv File, You can even store the query result in a CSV file. This will be useful to display the query, output in a tabular format. In the following example (EXAMPLE 15.12 -1) Using Python, script the student table is sorted “gender” wise in descending order and then arranged the, records alphabetically. The output of this Query will be written in a CSV file called “SQL.CSV”,, again the content is read from the CSV file and displayed the result., Example, import sqlite3, import io # to access replace(), import csv, # CREATING CSV FILE, d=open('c:/pyprg/sql.csv','w'), c=csv.writer(d), connection = sqlite3.connect("Academy.db"), cursor = connection.cursor(), # a=Connection.cursor(), cursor.execute("SELECT * FROM student ORDER BY GENDER DESC,SNAME"), # WRITING THE COLUMN HEADING, co = [i[0] for i in cursor.description], c.writerow(co), data=cursor.fetchall(), for item in data:, c.writerow(item), d.close(), # Reading the CSV File, # replace() is used to eliminate the newline character at the end of each row, with open('c:/pyprg/sql.csv', "r", newline=None) as fd:, # r = csv.reader(fd), for line in fd:, line = line.replace("\n", ""), print(line), cursor.close(), connection.close(), OUTPUT, Rollno,Sname,Grade,gender,Average,birth_date, 1, Akshay, B, M, 87.8, 2001-12-12, 2, Aravind, A, M, 92.5, 2000-08-17, 3, BASKAR, C, M, 75.2, 1998-05-17, 7, TARUN, D, M, 62.3, 1999-02-01, 5, VARUN, B, M, 80.6, 2001-03-14, 6, PRIYA, A, F, 98.6, 2002-01-01, 4, SAJINI, A, F, 95.6, 2002-11-01, XII Std Computer Science, , Chapter 15.indd 312, , 312, , 20-02-2019 15:40:10
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Example Opening the file (“sqlexcel.csv”) through MS-Excel and view the result, (Program is same similar to EXAMPLE 15.12 -1 script), import sqlite3, import io , #to access replace(), import csv, # database name to be passed as parameter, conn = sqlite3.connect("Academy.db"), print(“Content of the table before sorting and writing in CSV file”), cursor = conn.execute("SELECT * FROM Student"), for row in cursor:, print (row), # CREATING CSV FILE, d=open('c:\\pyprg\\sqlexcel.csv','w'), c=csv.writer(d), cursor = conn.cursor(), cursor.execute("SELECT * FROM student ORDER BY GENDER DESC,SNAME"), #WRITING THE COLUMN HEADING, co = [i[0] for i in cursor.description], c.writerow(co), data=cursor.fetchall(), for item in data:, c.writerow(item), d.close(), print(”sqlexcel.csv File is created open by visiting c:\\pyprg\\sqlexcel.csv”), conn.close(), , 313, , Chapter 15.indd 313, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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OUTPUT, Content of the table before sorting and writing in CSV file, (1, 'Akshay', 'B', 'M', 87.8, '2001-12-12'), (2, 'Aravind', 'A', 'M', 92.5, '2000-08-17'), (3, 'BASKAR', 'C', 'M', 75.2, '1998-05-17'), (4, 'SAJINI', 'A', 'F', 95.6, '2002-11-01'), (5, 'VARUN', 'B', 'M', 80.6, '2001-03-14'), (6, 'Priyanka', 'A', 'F', 98.6, '2002-01-01'), (7, 'TARUN', 'D', 'M', 62.3, '1999-02-01'), sqlexcel.csv File is created open by visiting c:\\pyprg\\sqlexcel.csv, OUTPUT THROUGH EXCEL, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, , A, Rollno, , B, Sname, , C, Grade, , D, gender, , E, Average, , F, birth_date, , 1 Akshay, , B, , M, , 87.8, , 2001-12-12, , 2 Aravind, , A, , M, , 92.5, , 2000-08-17, , 3 BASKAR, , C, , M, , 75.2, , 1998-05-17, , 7 TARUN, , D, , M, , 62.3, , 1999-02-01, , 5 VARUN, , B, , M, , 80.6, , 2001-03-14, , 6 PRIYA, , A, , F, , 98.6, , 2002-01-01, , 4 SAJINI, , A, , F, , 95.6, , 200-11-01, , 15.13 Table List, To show (display) the list of tables created in a database the following program (Example, refer page no 293) can be used., Example, import sqlite3, con = sqlite3.connect('Academy.db'), cursor = con.cursor(), cursor.execute("SELECT name FROM sqlite_master WHERE type='table';"), print(cursor.fetchall()), OUTPUT, [('Student',), ('Appointment',), ('Person',)], , XII Std Computer Science, , Chapter 15.indd 314, , 314, , 20-02-2019 15:40:10
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The above program (Example 15.3-1) display the names of all tables created in ‘Academy., db’ database. The master table holds the key information about your database tables and it, is called sqlite_master, So far, you have been using the Structured Query Language in Python scripts. This, chapter has covered many of the basic SQL commands. Almost all sql commands can be, executed by Python SQLite module. You can even try the other commands discussed in the, SQL chapter., , Points to remember:, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, •, , A database is an organized collection of data., Users of database can be human users, other programs or applications, SQLite is a simple relational database system, which saves its data in regular data files., Cursor is a control structure used to traverse and fetch the records of the database. All, the SQL commands will be executed using cursor object only., As data in a table might contain single or double quotes, SQL commands in Python, are denoted as triple quoted string., “Select” is the most commonly used statement in SQL, The SELECT Statement in SQL is used to retrieve or fetch data from a table in a database, The GROUP BY clause groups records into summary rows, The ORDER BY Clause can be used along with the SELECT statement to sort the data, of specific fields in an ordered way, Having clause is used to filter data based on the group functions., Where clause cannot be used along with ‘Group by’, The WHERE clause can be combined with AND, OR, and NOT operators, The ‘AND’ and ‘OR’ operators are used to filter records based on more than one, condition, Aggregate functions are used to do operations from the values of the column and a, single value is returned., COUNT() function returns the number of rows in a table., AVG() function retrieves the average of a selected column of rows in a table., SUM() function retrieves the sum of a selected column of rows in a table., MAX() function returns the largest value of the selected column., MIN() function returns the smallest value of the selected column, sqlite_master is the master table which holds the key information about your database, tables., The path of a file can be either represented as ‘/’ or using ‘\\’ in Python. For example, the path can be specified either as 'c:/pyprg/sql.csv', or c:\\pyprg\\sql.csv’., , 315, , Chapter 15.indd 315, , Data Manipulation through SQL, , 20-02-2019 15:40:10
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Hands on Experience, 1., , Create an interactive program to accept the details from user and store it in a csv file using, Python for the following table., Database name;- DB1, Table name : Customer, , 2., , Cust_Id, , Cust_Name, , Address, , Phone_no, , City, , C008, , Sandeep, , 14/1 Pritam Pura, , 41206819, , Delhi, , C010, , Anurag Basu, , 15A, Park Road, , 61281921, , Kolkata, , C012, , Hrithik, , 7/2 Vasant Nagar, , 26121949, , Delhi, , Consider the following table GAMES. Write a python program to display the records for, question (i) to (iv) and give outputs for SQL queries (v) to (viii), Table: GAMES, Gcode, , Name, , GameName, , Number, , PrizeMoney, , ScheduleDate, , 101, , Padmaja, , Carom Board, , 2, , 5000, , 01-23-2014, , 102, , Vidhya, , Badminton, , 2, , 12000, , 12-12-2013, , 103, , Guru, , Table Tennis, , 4, , 8000, , 02-14-2014, , 105, , Keerthana, , Carom Board, , 2, , 9000, , 01-01-2014, , 108, , Krishna, , Table Tennis, , 4, , 25000, , 03-19-2014, , (i) To display the name of all Games with their Gcodes in descending order of their schedule, date., (ii) To display details of those games which are having Prize Money more than 7000., (iii) To display the name and gamename of the Players in the ascending order of Gamename., (iv) To display sum of PrizeMoney for each of the Numberof participation groupings (as, shown in column Number 4), (v) Display all the records based on GameName, , XII Std Computer Science, , Chapter 15.indd 316, , 316, , 20-02-2019 15:40:11
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Evaluation, Part - I, , Choose the best answer, 1., , Which of the following is an organized collection of data?, (A) Database, , 2., , 3., , 4., , (1 Marks), (B) DBMS, , (C) Information, , (D) Records, , SQLite falls under which database system?, (A) Flat file database system, , (B) Relational Database system, , (C) Hierarchical database system, , (D) Object oriented Database system, , Which of the following is a control structure used to traverse and fetch the records of the, database?, (A) Pointer , , (B) Key, , (C) Cursor , , (D) Insertion point, , Any changes made in the values of the record should be saved by the command, (A) Save, , (B) Save As, , (C) Commit, , (D) Oblige, , 5. Which of the following executes the SQL command to perform some action?, (A) Execute(), 6., , 8., , 9., , (C) Cursor(), , (D) run(), , Which of the following function retrieves the average of a selected column of rows in a, table?, (A) Add(), , 7., , (B) Key(), , (B) SUM(), , (C) AVG(), , (D) AVERAGE(), , The function that returns the largest value of the selected column is, (A) MAX() , , (B) LARGE(), , (C) HIGH() , , (D) MAXIMUM(), , Which of the following is called the master table?, (A) sqlite_master , , (B) sql_master, , (C) main_master , , (D) master_main, , The most commonly used statement in SQL is, (A) cursor, , (B) select, , (C) execute, , (D) commit, , 10. Which of the following clause avoide the duplicate?, (A) Distinct, , (B) Remove, , (C) Where, , 317, , Chapter 15.indd 317, , (D) GroupBy, , Data Manipulation through SQL, , 20-02-2019 15:40:11
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Part - II, , Answer the following questions, , (2 Marks), , 1., , Mention the users who uses the Database., , 2., , Which method is used to connect a database? Give an example., , 3., , What is the advantage of declaring a column as “INTEGER PRIMARY KEY”, , 4., , Write the command to populate record in a table. Give an example., , 5., , Which method is used to fetch all rows from the database table?, Part - III, , Answer the following questions, , (3 Marks), , 1., , What is SQLite?What is it advantage?, , 2., , Mention the difference between fetchone() and fetchmany(), , 3., , What is the use of Where Clause.Give a python statement Using the where clause., , 4., , Read the following details.Based on that write a python script to display department wise, records, database name :- organization.db, Table name, , :- Employee, , Columns in the table :- Eno, EmpName, Esal, Dept, 5., , Read the following details.Based on that write a python script to display records in, desending order of, Eno, database name :- organization.db, Table name, , :- Employee, , Columns in the table :- Eno, EmpName, Esal, Dept, Part - IV, , Answer the following questions, , (5 Marks), , 1., , Write in brief about SQLite and the steps used to use it., , 2., , Write the Python script to display all the records of the following table using fetchmany(), Icode, , ItemName, , Rate, , 1003, , Scanner, , 10500, , 1004, , Speaker, , 3000, , XII Std Computer Science, , Chapter 15.indd 318, , 318, , 20-02-2019 15:40:11
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1005, , Printer, , 8000, , 1008, , Monitor, , 15000, , 1010, , Mouse, , 700, , 3., , hat is the use of HAVING clause. Give an example python script, , 4., , Write a Python script to create a table called ITEM with following specification., Add one record to the table., Name of the database :- ABC, Name of the table :- Item, Column name and specification :-, , 5., , Icode, , :-, , integer and act as primary key, , Item Name, , :-, , Character with length 25, , Rate, , :-, , Integer, , Record to be added, , :-, , 1008, Monitor,15000, , Consider the following table Supplier and item .Write a python script for (i) to (ii), SUPPLIER, Suppno, , Name, , City, , Icode, , SuppQty, , S001, , Prasad, , Delhi, , 1008, , 100, , S002, , Anu, , Bangalore, , 1010, , 200, , S003, , Shahid, , Bangalore, , 1008, , 175, , S004, , Akila, , Hydrabad, , 1005, , 195, , S005, , Girish, , Hydrabad, , 1003, , 25, , S006, , Shylaja, , Chennai, , 1008, , 180, , S007, , Lavanya, , Mumbai, , 1005, , 325, , i) Display Name, City and Itemname of suppliers who do not reside in Delhi., ii) Increment the SuppQty of Akila by 40, References, 1., , The Definitive Guide to SQLite by Michael Owens, , 2., , Programming for Beginners: 2 Manuscripts: SQL & Python by Byron Francis, , 3., , Tutorialspoint.com, 319, , Chapter 15.indd 319, , Data Manipulation through SQL, , 20-02-2019 15:40:11
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Unit, , V, , CHAPTER 16, DATA VISUALIZATION USING PYPLOT:, LINE CHART, PIE CHART AND BAR CHART, , Learning Objectives, After learning this chapter, the learners will be able to, • Define the term Data Visualization., • List the types of Data Visualization., • List the uses of Data Visualization., • List the types of Visualizations in Matplotlib., • Practice installing Matplotlib., • Explore importing Matplotlib., • Classify the types of Data Visualization plots., • Practice creating various types of plots using Matplotlib., , 16.1 Data Visualization Definition, Data Visualization is the graphical representation of information and data. The, objective of Data Visualization is to communicate information visually to users. For this, data, visualization uses statistical graphics. Numerical data may be encoded using dots, lines, or, bars, to visually communicate a quantitative message., General types of Data Visualization, • Charts, • Tables, • Graphs, • Maps, • Infographics, • Dashboards, Data visualization - Uses, • Data Visualization help users to analyze and interpret the data easily., XII Std Computer Science, , Chapter 16.indd 320, , 320, , 20-02-2019 15:43:23
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• It makes complex data understandable and usable., • Various Charts in Data Visualization helps to show relationship in the data for one or more, variables., Infographics → An infographic (information graphic) is the representation of, information in a graphic format., Dashboard → A dashboard is a collection of resources assembled to create a single unified, visual display. Data visualizations and dashboards translate complex ideas and concepts, into a simple visual format. Patterns and relationships that are undetectable in text are, detectable at a glance using dashboard., Introduction to Matplotlib — Data Visualization in Python, Matplotlib is the most popular data visualization library in Python. It allows you to, create charts in few lines of code., Types of Visualizations in Matplotlib, There are many types of Visualizations under Matplotlib. Some of them are:, • Line plot, • Scatter plot, • Histogram, • Box plot, • Bar chart and, • Pie chart, Scatter plot: A scatter plot is a type of plot that shows the data as a collection of, points. The position of a point depends on its two-dimensional value, where each, value is a position on either the horizontal or vertical dimension., Box plot: The box plot is a standardized way of displaying the distribution of data based, on the five number summary: minimum, first quartile, median, third quartile, and, maximum., Installing Matplotlib, You can install matplotlib using pip. Pip is a management software for installing python, packages., , 321, , Chapter 16.indd 321, , Data Visualization using Pyplot, , 20-02-2019 15:43:23
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Note, Detailed installation procedures given in Annexure, , 16.2 Getting Started, After installing Matplotlib, we will begin coding by importing Matplotlib using the, command:, import matplotlib.pyplot as plt, Now you have imported Matplotlib in your workspace. You need to display the plots., Using Matplotlib from within a Python script, you have to add plt.show() method inside the, file to display your plot., , Example, import matplotlib.pyplot as plt, plt.plot([1,2,3,4]), plt.show(), , Output, This window is a matplotlib window, which allows you to see your graph. You, can hover the graph and see the coordinates in the bottom right., , 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, 0.0, , 0.5, , 1.0, , 1.5, , 2.0, , 2.5, , 3.0, , Figure 16.1, XII Std Computer Science, , Chapter 16.indd 322, , 322, , 20-02-2019 15:43:24
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You may be wondering why the x-axis ranges from 0-3 and the y-axis from 1-4. If you, provide a single list or array to the plot () command, matplotlib assumes it is a sequence of y, values, and automatically generates the x values for you. Since python ranges start with 0, the, default x vector has the same length as y but starts with 0. Hence the x data are [0, 1, 2, 3]., plot() is a versatile command, and will take an arbitrary number of arguments., , Program, For example, to plot x versus y, you can issue the command:, import matplotlib.pyplot as plt, plt.plot([1,2,3,4], [1,4,9,16]), plt.show(), This .plot takes many parameters, but the first two here are 'x' and 'y' coordinates. This, means, you have 4 co-ordinates according to these lists: (1,1), (2,4), (3,9) and (4,16)., , 16, 14, 12, 10, 8, 6, 4, 2, , 1.0, , 1.5, , 2.0, , 2.5, , 3.0, , 3.5, , 4.0, , Figure 16.2, , 323, , Chapter 16.indd 323, , Data Visualization using Pyplot, , 20-02-2019 15:43:24
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Plotting Two Lines, To plot two lines, use the following code:, import matplotlib.pyplot as plt, x = [1,2,3], y = [5,7,4], x2 = [1,2,3], y2 = [10,14,12], plt.plot(x, y, label='Line 1'), plt.plot(x2, y2, label='Line 2'), plt.xlabel('X-Axis'), plt.ylabel('Y-Axis'), plt.title('LINE GRAPH'), plt.legend(), plt.show(), Output, With plt.xlabel and plt.ylabel, you can assign labels to those respective axis. Next, you, can assign the plot's title with plt.title, and then you can invoke the default legend with plt., legend()., , LINE GRAPH, 14, , Line1, Line2, , Y - Axis, , 12, 10, 8, , 6, 4, 1.00, , 1.25, , 1.50, , 1.75, , 2.00, 2.25, X - Axis, , 2.50, , 2.75, , 3.00, , Figure 16.3, XII Std Computer Science, , Chapter 16.indd 324, , 324, , 20-02-2019 15:43:24
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Buttons in the output, In the output figure, you can see few buttons at the bottom left corner. Let us see the use, of these buttons., , Home Button, , Pan Axis Button, , Zoom, Button, , Forward / Back Buttons, , Configure, Subplots, Button, , Save the, Figure Button, , Figure 16.4, Home Button → The Home Button will help once you have begun navigating your chart. If, you ever want to return back to the original view, you can click on this., Forward/Back buttons → These buttons can be used like the Forward and Back buttons in, your browser. You can click these to move back to the previous point you were at, or forward, again., Pan Axis → This cross-looking button allows you to click it, and then click and drag your, graph around., Zoom → The Zoom button lets you click on it, then click and drag a square that you would like, to zoom into specifically. Zooming in will require a left click and drag. You can alternatively, zoom out with a right click and drag., Configure Subplots → This button allows you to configure various spacing options with your, figure and plot., Save Figure → This button will allow you to save your figure in various forms., , 16.3 Special Plot Types, Matplotlib allows you to create different kinds of plots ranging from histograms and, scatter plots to bar graphs and bar charts., Line Chart, A Line Chart or Line Graph is a type of chart which displays information as a series of, data points called ‘markers’ connected by straight line segments. A Line Chart is often used, to visualize a trend in data over intervals of time – a time series – thus the line is often drawn, chronologically., 325, , Chapter 16.indd 325, , Data Visualization using Pyplot, , 20-02-2019 15:43:24
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Example: Line plot, import matplotlib.pyplot as plt, years = [2014, 2015, 2016, 2017, 2018], total_populations = [8939007, 8954518, 8960387, 8956741, 8943721], plt.plot (years, total_populations), plt.title ("Year vs Population in India"), plt.xlabel ("Year"), plt.ylabel ("Total Population"), plt.show(), In this program,, Plt.title() → specifies title to the graph, Plt.xlabel() → specifies label for X-axis, Plt.ylabel() → specifies label for Y-axis, Output, Year vs Population in India, 8960000, , 8955000, , 8950000, , 8945000, , 8940000, 2014.4 2014.5 2015.0 2015.5 2016.0 2016.6 2017.0 2017.7 2018.0, Year, , Figure 16.5, Bar Chart, A BarPlot (or BarChart) is one of the most common type of plot. It shows the, relationship between a numerical variable and a categorical variable., Bar chart represents categorical data with rectangular bars. Each bar has a height, corresponds to the value it represents. The bars can be plotted vertically or horizontally., It’s useful when we want to compare a given numeric value on different categories. To, make a bar chart with Matplotlib, we can use the plt.bar() function., XII Std Computer Science, , Chapter 16.indd 326, , 326, , 20-02-2019 15:43:24
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Example, import matplotlib.pyplot as plt, # Our data, labels = ["TAMIL", "ENGLISH", "MATHS", "PHYSICS", "CHEMISTRY", "CS"], usage = [79.8, 67.3, 77.8, 68.4, 70.2, 88.5], # Generating the y positions. Later, we'll use them to replace them with labels., y_positions = range (len(labels)), # Creating our bar plot, plt.bar (y_positions, usage), plt.xticks (y_positions, labels), plt.ylabel ("RANGE"), plt.title ("MARKS"), plt.show(), Output, MARKS, , RANGE, , 80, 60, 40, 20, 0, , TAMIL, , ENGLISH, , MATHS PHYSICS CHEMISTRY, , CS, , Figure 16.6, The above code represents the following:, Labels → Specifies labels for the bars., Usgae → Assign values to the labels specified., Xticks → Display the tick marks along the x-axis at the values represented. Then specify, the label for each tick mark., Range → Create sequence of numbers., 327, , Chapter 16.indd 327, , Data Visualization using Pyplot, , 20-02-2019 15:43:24
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Bar Graph and Histogram are the two ways to display data in the form of a diagram., Key Differences Between Histogram and Bar Graph, The differences between Histogram and bar graph are as follows, 1. Histogram refers to a graphical representation; that displays data by way of bars to, show the frequency of numerical data. A bar graph is a pictorial representation of data, that uses bars to compare different categories of data., 2. A histogram represents the frequency distribution of continuous variables. Conversely,, a bar graph is a diagrammatic comparison of discrete variables., 3. Histogram presents numerical data whereas bar graph shows categorical data., 4. The histogram is drawn in such a way that there is no gap between the bars. On the ot her, hand, there is proper spacing between bars in a bar graph that indicates discontinuity., 5. Items of the histogram are numbers, which are categorised together, to represent ranges, of data. As opposed to the bar graph, items are considered as individual entities., 6. In the case of a bar graph, it is quite common to rearrange the blocks, from highest to, lowest. But with histogram, this cannot be done, as they are shown in the sequence of, classes., 7. The width of rectangular blocks in a histogram may or may not be same while the, width of the bars in a bar graph is always same., Pie Chart, Pie Chart is probably one of the most common type of chart. It is a circular graphic, which is divided into slices to illustrate numerical proportion. The point of a pie chart is, to show the relationship of parts out of a whole., To make a Pie Chart with Matplotlib, we can use the plt.pie() function. The autopct, parameter allows us to display the percentage value using the Python string formatting., Example, import matplotlib.pyplot as plt, sizes = [89, 80, 90, 100, 75], labels = ["Tamil", "English", "Maths", "Science", "Social"], plt.pie (sizes, labels = labels, autopct = "%.2f "), plt.axes().set_aspect ("equal"), plt.show(), XII Std Computer Science, , Chapter 16.indd 328, , 328, , 20-02-2019 15:43:24
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Output, , English, Tamil, , 18.43, 20.51, Maths, , 20.74, 17.28, 23.04, , Social, , Science, , Figure 16.7, , Hands on Practice, 1., , Create a plot. Set the title, the x and y labels for both axes., , 2., , Plot a pie chart for your marks in the recent examination., , 3., , Plot a line chart on the academic performance of Class 12 students in Computer, Science for the past 10 years., , 4., , Plot a bar chart for the number of computer science periods in a week., , 329, , Chapter 16.indd 329, , Data Visualization using Pyplot, , 20-02-2019 15:43:25
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Evaluation, Part - I, , Choose the best answer, , (1 Marks), , 1. Which is a python package used for 2D graphics?, a. matplotlib.pyplot, , b. matplotlib.pip, , c. matplotlib.numpy, , d. matplotlib.plt, , 2. Identify the package manager for Python packages, or modules., a. Matplotlib , 3., , b. PIP , , c. plt.show() , , d. python package, , Read the following code: Identify the purpose of this code and choose the right, option from the following., C:\Users\YourName\AppData\Local\Programs\Python\Python36-32\Scripts>pip –, version, , 4., , a. Check if PIP is Installed, , b. Install PIP, , c. Download a Package, , d. Check PIP version, , Read the following code: Identify the purpose of this code and choose the right, option from the following., C:\Users\Your, list, , 5., , Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip, , a. List installed packages, , b. list command, , c. Install PIP, , d. packages installed, , To install matplotlib, the following function will be typed in your command prompt., What does “-U”represents?, Python –m pip install –U pip, a. downloading pip to the latest version, b. upgrading pip to the latest version, c. removing pip, d. upgrading matplotlib to the latest version, , 6. Observe the output figure. Identify the coding for obtaining this output., , XII Std Computer Science, , Chapter 16.indd 330, , 330, , 20-02-2019 15:43:25
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a., , b., , Epic Info, , 16, , 1, , 16, 14, , 14, , info, , 12, , y axis, , Y axis, , 12, , 10, , 10, , 2 6, , 4, , 8, 6, , 8, , 2, 5, , 7, , 6, , 8, , X axis, , 9, , 10, , 2, , 3, , 3, , 11, , c., , 4, , 5, , x axis, , 7, , 6, , d., , 2.100, , 4.0, , 2.075, , 3.5, , some numbers, , 2.050, 2.025, 2.000, 1.975, 1.950, , 3.0, 2.5, 2.0, 1.5, , 1.925, , 1.0, , 1.900, 2.85, , 2.90, , 2.95, , 3.00, , 3.05, , 3.10, , 0.0, , 3.15, , 0.0, , 0.5, , 1.5, , 2.0, , 2.5, , 3.0, , 8. Which key is used to run the module?, a. F6, , b. F4, , c. F3, , d. F5, , 9. Identify the right type of chart using the following hints., Hint 1: This chart is often used to visualize a trend in data over intervals of time., Hint 2: The line in this type of chart is often drawn chronologically., a. Line chart, , b. Bar chart, , c. Pie chart, , d. Scatter plot, , 10. Read the statements given below. Identify the right option from the following for pie, chart., Statement A: To make a pie chart with Matplotlib, we can use the plt.pie() function., Statement B: The autopct parameter allows us to display the percentage value using, the Python string formatting., a. Statement A is correct, , b. Statement B is correct, , c. Both the statements are correct, , d. Both the statements are wrong, Part - II, , Answer the following questions, , (2 Marks), , 1., , Define: Data Visualization., , 2., , List the general types of data visualization., , 3., , List the types of Visualizations in Matplotlib., , XII Std Computer Science, , Chapter 16.indd 332, , 332, , 20-02-2019 15:43:25
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4., , How will you install Matplotlib?, , 5., , Write the difference between the following functions: plt.plot([1,2,3,4]), plt., plot([1,2,3,4],, [1,4,9,16])., Part - III, , Answer the following questions, 1., , (3 Marks), , Draw the output for the following data visualization plot., import matplotlib.pyplot as plt, plt.bar([1,3,5,7,9],[5,2,7,8,2], label="Example one"), plt.bar([2,4,6,8,10],[8,6,2,5,6], label="Example two", color='g'), plt.legend(), plt.xlabel('bar number'), plt.ylabel('bar height'), plt.title('Epic Graph\nAnother Line! Whoa'), plt.show(), , 2., , Write any three uses of data visualization., , 3., , Write the coding for the following:, a. To check if PIP is Installed in your PC., b. To Check the version of PIP installed in your PC., c. To list the packages in matplotlib., , 4., , Write the plot for the following pie chart output., , 29.2%, 54.2%, 8.3%, 8.3%, , 333, , Chapter 16.indd 333, , Data Visualization using Pyplot, , 20-02-2019 15:43:25
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GLOSSARY, Terminology, , Meaning, , Access control, , security technique that regulates who or what can view, or use resources in a computing environment, , Access modifiers, , Private , Protected and Public, , append(), , Used to add an element in a list, , Argument, , Argument is the actual value of this variable that gets, passed to function., , argv, , An array containing the values passed through, command line argument, , Attribute, , Data items that makes up an object, , Authorization, , Giving permission or access, , Block, , Set of Statements, , Boolean, , means Logical, , break, , Exit the control, , c = sqlite3.connect('test. db'), , create a database connection to the SQLite database, ‘test.db’. You can also supply the special name :memory:, to create a database in RAM., , c.close(), , To release the connection of the database, , c.commit(), , To save the changes made in the table, , c.execute(), , Executes all SQL commands .Accepts two kinds of, placeholders: question marks ? (“qmark style”) and, named placeholders :name (“named style”)., , Cartesian product, , Cartesian operation is helpful to merge columns from, two relations, , cd, , cd command refers to change directory, , Class, , Template of creating objects., , Class variable, , An ordinary variable declared inside a class, , cls, , To clear the screen in command window, , Comma(,), , Comma is used to separate each data in a csv file, , 335, , Glossary.indd 335, , 20-02-2019 15:44:16
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compiler, , Scans the entire program and translates it as a whole, into machine code. It generates the error message only, after scanning the whole program. Hence debugging is, comparatively hard., , Conjunction, , Concurrence, coincidence, , Constraint, , Restriction or limitation, , Constructor, , A special function get execution automatically when, an object enter into scope., , continue, , To skip the remaining part and start with next iteration., , CRUD, , Create, Read, Update and Delete, , csv.reader(), , The reader function is designed to take each line of the, file and make a list of all columns, , csv.register_dialect(), , A dialect describes the format of the csv file that is to, be read, , CsvQuote All, , If quoting is set to csvquote all, then writerow() will, quote all fields., , cur = c.cursor(), , Creating cursor object, , cur.fetchall(), , method to get a list of the matching rows., , cur.fetchmany(), , method that returns the next number of rows (n) of the, result set, , cur.fetchone(), , method to retrieve a single matching row, , CWI, , Centrum Wiskunde & Informatica, , DBA, , DataBase Adminstrator, , DBMS, , Database Management System, , def, , This keyword is used to define function., , Destructor, , A special function get execution automatically when, an object exit from its scope., , dict(), , It is used to print the data in dictionary format without, orderdict, , Dictionary, , Collection of Key-Value pairs, , DictReader(), , Works by reading in the first line of the CSV and using, each column comma separated value in this line as a, dictionary key., , Dictwriter(), , Write dictionary data into a CSV file, , elif, , else…if, , Embedded, , Firmly attached, , Enter key, , Enter key or newline is used to create rows in a csv file, 336, , Glossary.indd 336, , 20-02-2019 15:44:17
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eval(), , This function is used to evaluate the value of a string., , Father of Relational Database Dr. Edgar Frank Codd, g++, , compiler to compile c++ program, , GIS, , Geographic Information System, , global Scope, , A variable, with global scope can be used anywhere in, the program., , Glue language, , You do not write the complete application in the, language, but rather, you use the language to, orchestrate(organize) modules written in (possibly, many different) other languages, making them work, together to form the application. A glue language, makes it easy to do that (convenient syntax, good, support for inter-process communication and data, managing, no compilation step etc)., , id (), , It returns the memory address of the given object., , IDLE, , Integrated Development Environment, , immutable, , unchangeable, , Implementation, , Implementation carries out the operation declared in, the interfac, , import, , Import in python is similar to #include header_file, in C++. Python modules can get access to code from, another module by importing the file/function using, “import” statement., , Impure Functions, , Any function that changes the internal state of one of, its arguments or the value of some external variable is, an impure function., , Instantiation, , Process of creating an object, , Integrity, , Whole and undivided, , Interactive Mode, , A way of using the Python interpreter by typing, command and expressions at the prompt., , Interface, , Interface defines what an object can do, but doesn't, actually do it, , interpreter, , Translates program one statement at a time. It, continues translating the program until the first error, is met, in which case it stops. Hence debugging is easy., , Intersection, , Intersection defines a relation consisting of a set of all, tuple that are in both A and B., , Key, , Data that is mapped to a value in a dictionary, 337, , Glossary.indd 337, , 20-02-2019 15:44:17
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lambda, , Lambda function is mostly used for creating small and, one- time anonymous function., , LEGB rule, , Local → Enclosed → Global → Built-in scope, , List, , Mutable ordered collection of values, , local Scope, , A variable declared inside the function's body or in a, block is called local scope., , Looping, , Repetition, , Mapping, , The process of binding a variable name with an object, , Method, , A function declared and defined inside a class., A module is a file containing Python definitions and, statements. The file name is the module name with the, suffix .py appended. Within a module, the module’s, name (as a string) is available as the value of the global, variable name ., , module, , Namespaces, , containers for mapping names of variables to objects, , Nested Block, , A block within a block is called nested block., , next(), , The next() function returns the next item from the, iterator. It can also be used to skip a row of the csv file, , Object, , Collection of Data and Functions., , Object, Programming, , Oriented Computer Programming concept based on real world, objects., , operator.itemgetter(col_ no), , To sort by more than one column from a csv file, , os.system(), , Used to execute system command and here in our, python program is used to compile the c++ program, using g++, , Parameter, , Parameter is variable in the declaration of function, definition., , parse, , To split an input into pieces of data that can be easily, stored or manipulated., , pass, , Can be used as placeholder in functions and loops., , Projection ( π ), , The projection eliminates all attributes of the input, relation but those mentioned in the projection list, , Prompt, , Character (<<<) displayed by the interpreter to, indicate that it is ready to take input from the user., , Pure Functions, , Pure functions always returns the same result if the, same arguments are passed in, , Python prompt, , >>>, 338, , Glossary.indd 338, , 20-02-2019 15:44:17
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Queue, , Queue is an abstract data structure, somewhat similar, to Stacks. Unlike stacks, a queue is open at both its, ends. One end is always used to insert data(enqueue), and the other is used to remove data(dequeue). Queue, follows First-In-First-Out methodology, i.e., the data, item stored first will be accessed first., , RDBMS, , Relational Database Management System, , recursion, , When a function calls itself is known as recursion., , Redundant, , Duplication of data, , Routines, , routines are otherwise called as functions or methods., In Python it is also called as definition, , Schema, , Structure or model, , Scope, , Visibility of variables, parameters and functions in, one part of a program to another part of the same, program., , Script, , A Python program stored in a file., , Script Mode, , A way of using the Python interpreter by typing, command and expressions at the prompt., , Select ( σ ), , The SELECT operation is used for selecting a subset of, the tuples according to a given selection condition, , Selectors, , Functions that retrieve information from the data, type., , Sequential, , One after another, , Set difference(-), , (-) symbol denotes it. The result of A-B is a relation, which includes all tuples that are in A but not in B., , skipinitialspace=true, , When true, whitespace immediately following the, delimeter is ignored. The default is false, , slicing, , cut, , Stack, , A stack (sometimes called a “push-down stack”) is an, ordered collection of items where the addition of new, items and the removal of existing items always takes, place at the same end. This end is commonly referred, to as the “top.” The end opposite the top is known as, the “base.This ordering principle is sometimes called, LIFO, last- in first-out., , stride, , a long step, , string, , sequence of letters, numbers or symbols, , subscript, , an index number, 339, , Glossary.indd 339, , 20-02-2019 15:44:17
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Syntax, , The structure of a program, , Syntax Error, , An error in a program that makes it impossible to, parse., , Token, , One of the basic elements of the syntactic structure, of a program., , Tuple, , It is a sequence of immutable(not changeable) objects., Tuples are sequences, just like lists.Tuples are defined, by having values between parentheses ( )., , Union operation(U), , Union is symbolized by symbol. It includes all tuples, that are in tables A or in B., , variable, , Memory box to store values, , writer ow(), , Method to write a single row of data in a file, , writer ows(), , Method to write multiple rows of data in a file, , FALSE, , Logical value 0, , TRUE, , Logical value 1, , 340, , Glossary.indd 340, , 20-02-2019 15:44:17
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ANNEXURE - 1, , Function, , abs(), all(), any(), ascii(), bin(), bool(), bytearray(), bytes(), callable(), chr(), classmethod(), compile(), complex(), delattr(), dir(), divmod(), enumerate(), eval(), exec(), filter(), float(), format(), getattr(), globals(), hasattr(), hash(), help(), hex(), id(), isinstance(), issubclass(), iter(), len(), locals(), map(), max(), memoryview(), min(), next(), object(), oct(), , List of Python Functions, I. Built-in Functions, , Description, returns absolute value of a number, returns true when all elements in iterable is true, Checks if any Element of an Iterable is True, Returns String Containing Printable Representation, converts integer to binary string, Converts a Value to Boolean, returns array of given byte size, returns immutable bytes object, Checks if the Object is Callable, Returns a Character (a string) from an Integer, returns class method for given function, Returns a Python code object, Creates a Complex Number, Deletes Attribute From the Object, Tries to Return Attributes of Object, Returns a Tuple of Quotient and Remainder, Returns an Enumerate Object, Runs Python Code Within Program, Executes Dynamically Created Program, constructs iterator from elements which are true, returns floating point number from number, string, returns formatted representation of a value, returns value of named attribute of an object, returns dictionary of current global symbol table, returns whether object has named attribute, returns hash value of an object, Invokes the built-in Help System, Converts to Integer to Hexadecimal, Returns Identify of an Object, Checks if a Object is an Instance of Class, Checks if a Object is Subclass of a Class, returns iterator for an object, Returns Length of an Object, Returns dictionary of a current local symbol table, Applies Function and Returns a List, returns largest element, returns memory view of an argument, returns smallest element, Retrieves Next Element from Iterator, Creates a Featureless Object, converts integer to octal, 341, , Annexure I & 2.indd 341, , 20-02-2019 14:35:27
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open(), ord(), pow(), print(), property(), range(), repr(), reversed(), round(), set(), setattr(), slice(), sorted(), staticmethod(), str(), sum(), super(), type(), vars(), __import__(), , Returns a File object, returns Unicode code point for Unicode character, returns x to the power of y, Prints the Given Object, returns a property attribute, return sequence of integers between start and stop, returns printable representation of an object, returns reversed iterator of a sequence, rounds a floating point number to ndigits places., returns a Python set, sets value of an attribute of object, creates a slice object specified by range(), returns sorted list from a given iterable, creates static method from a function, returns informal representation of an object, Add items of an Iterable, Allow you to Refer Parent Class by super, Returns Type of an Object, Returns __dict__ attribute of a class, Advanced Function Called by import, , II. String Functions, Function, capitalize(), casefold(), center(), count(), encode(), endswith(), expandtabs(), find(), format(), format_map(), index(), input(), int(), isalnum(), isalpha(), isdecimal(), isdigit(), isidentifier(), islower(), isnumeric(), isprintable(), isspace(), , Description, Converts first character to Capital Letter, converts to casefolded strings, Pads string with specified character, returns occurrences of substring in string, returns encoded string of given string, Checks if String Ends with the Specified Suffix, Replaces Tab character With Spaces, Returns the index of first occurrence of substring, formats string into nicer output, Formats the String Using Dictionary, Returns Index of Substring, reads and returns a line of string, returns integer from a number or string, Checks Alphanumeric Character, Checks if All Characters are Alphabets, Checks Decimal Characters, Checks Digit Characters, Checks for Valid Identifier, Checks if all Alphabets in a String are Lowercase, Checks Numeric Characters, Checks Printable Character, Checks Whitespace Characters, 342, , Annexure I & 2.indd 342, , 20-02-2019 14:35:27
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istitle(), isupper(), join(), ljust(), lower(), lstrip(), maketrans(), partition(), replace(), rfind(), rindex(), rjust(), rpartition(), rsplit(), rstrip(), slice(), split(), splitlines(), startswith(), strip(), swapcase(), title(), translate(), upper(), zfill(), , Checks for Titlecased String, returns if all characters are uppercase characters, Returns a Concatenated String, returns left-justified string of given width, returns lowercased string, Removes Leading Characters, returns a translation table, Returns a Tuple, Replaces Substring Inside, Returns the Highest Index of Substring, Returns Highest Index of Substring, returns right-justified string of given width, Returns a Tuple, Splits String From Right, Removes Trailing Characters, creates a slice object specified by range(), Splits String from Left, Splits String at Line Boundaries, Checks if String Starts with the Specified String, Removes Both Leading and Trailing Characters, swap uppercase characters to lowercase; vice versa, Returns a Title Cased String, returns mapped charactered string, returns uppercased string, Returns a Copy of The String Padded With Zeros, , III. List Functions, Function, append(), clear(), copy(), count(), extend(), index(), insert(), list() Function, pop(), remove(), reverse(), slice(), sort(), , Description, Add Single Element to The List, Removes all Items from the List, Returns Shallow Copy of a List, returns occurrences of element in a list, Add Elements of a List to Another List, returns smallest index of element in list, Inserts Element to The List, creates list in Python, Removes Element at Given Index, Removes Element from the List, Reverses a List, creates a slice object specified by range(), sorts elements of a list, 343, , Annexure I & 2.indd 343, , 20-02-2019 14:35:27
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IV. Tuple Functions, Function, count(), index(), slice(), tuple() Function, zip(), , Description, returns occurrences of element in a tuple, returns smallest index of element in tuple, creates a slice object specified by range(), Creates a Tuple, Returns an Iterator of Tuples, , V. Set Functions, Function, , add(), clear(), copy(), difference(), difference_update(), discard(), frozenset(), intersection(), intersection_update(), isdisjoint(), issubset(), issuperset(), pop(), remove(), set(), symmetric_difference(), symmetric_difference_update(), union(), update(), , Description, , adds element to a set, remove all elements from a set, Returns Shallow Copy of a Set, Returns Difference of Two Sets, Updates Calling Set With Intersection of Sets, Removes an Element from The Set, returns immutable frozenset object, Returns Intersection of Two or More Sets, Updates Calling Set With Intersection of Sets, Checks Disjoint Sets, Checks if a Set is Subset of Another Set, Checks if a Set is Superset of Another Set, Removes an Arbitrary Element, Removes Element from the Set, returns a Python set, Returns Symmetric Difference, Updates Set With Symmetric Difference, Returns Union of Sets, Add Elements to The Set., , VI. Dictionary Functions, clear(), copy(), dict(), fromkeys(), get(), items(), keys(), pop(), popitem(), setdefault(), update(), values(), , Function, , Description, , Removes all Items, Returns Shallow Copy of a Dictionary, Creates a Dictionary, creates dictionary from given sequence, Returns Value of The Key, returns view of dictionary's (key, value) pair, Returns View Object of All Keys, removes and returns element having given key, Returns & Removes Element From Dictionary, Inserts Key With a Value if Key is not Present, Updates the Dictionary, returns view of all values in dictionary, 344, , Annexure I & 2.indd 344, , 20-02-2019 14:35:27
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ANNEXURE - II, Installation of MySQL and Creating a database, • Download WAMP based on system configuration and install it in your computer., , • log on to MySQL console as user (root)., • Enter password appears (No need to enter password), press Enter key., • MySQL prompt appears from where you can enter the SQL commands., C:\wamp\bin\mysql\mysql5.7.23\bin\mysql.exe, , Enter password, Welcome to the My SQL monitor. Commands end with ; or \g., Your MYSQL connection id is 2, Server Version: 5.7.23 MYSQL Community Server <GPL>, Copyright <c> 2000, 2018, Oracle and\or its affiliates. All rights reserved., Oracle is a registered trademark of Oracle Corporation and\or its, affiliates. Other names may be trademarks of their respective, owners., Type 'help;' or '\h' for help. Type '\c' to clear the current input statement., Mysql>, , 345, , Annexure I & 2.indd 345, , 20-02-2019 14:35:27
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ANNEXURE 3, Installation of MinGW, STEPS TO INSTALL MinGW-w64 - for 32 and 64 bit Windows, STEP1:, , Type https://sourceforge.net/projects/mingw-w64 in any search engine(www., google.in) and double click it., , Step 2 :, , Click the Download button which appears in the home page. The file should start, downloading in your standard download folder or it prompts the save as dialog box, , Step 3 :, , The file should appear as, . Terminate the window browsing the, SourceForge web site. Move this file to a more permanent location, so that you can, install MinGW (and reinstall it later, if necessary)., 346, , Annexure III.indd 346, , 20-02-2019 14:34:38
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step 4:, , Start the Installation as per the instructions given bellow., , Installing:, 1., , Double-click the, , . icon. The following pop-up window will appear., , 2., , Click Run. The following pop-up window will appear. Click next button in the following, window, , Welcome to the MinGW-W64, Intallation!, Welcome to the MinGW-W64 online installer., , 3., , The following pop-up window will appear, which specify the Setup settings, , 347, , Annexure III.indd 347, , 20-02-2019 14:34:38
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Settings, Specify setup settings., Version, Architecture, Threads, Exception, Build revision, , 8.1.0, i686, posix, dwarf, 0, , < Back, , 4., , Cancel, , Select the destination folder in the following window to install MinGW-W64. Click next, button, Installation floder, , Select a destination folder where i686-8.1.0-posix-dwarf-rf_v6-rev0 will, be installed., , Setup will install files in the following folder., In you would like to install i686-8.1.0-posix-dwarf-rt_v6-rev0 in to different, folder, click Browser and select another folder., Destination folder, , C:\Program Files (x86)\mingw-w6-i686-8.1.0-posix-dw, , Browser ..., , Space available: 96.80 GB, Create shortcuts in Start Menu, , 5., , Select the destination folder in the following window to install MinGW-W64., , 348, , Annexure III.indd 348, , 20-02-2019 14:34:38
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6., , Wait for the completion of installation, Installing Files, Copying i686-8.1.0-posix-dwarf-rt_v6-rev0 files to your computer., , To stop or pause the installation process, click Cancel., , Downloading file..., File: i686-8.1.0-release-posix-dwarf-rt_v6-rev0.7z, , 7, , Click the button once it gets highlighted., Installing Files, Copying i686-8.1.0-posix-dwarf-rt_v6-rev0 files to your computer., , Click Next to continue the installation., , 8., , Locate the folder in your PC. For example here the mingw64 is present in the following, path c:\Program Files\mingw-w64., , 9., , Open the folder and double click the batch file. The program will get executed., , 349, , Annexure III.indd 349, , 20-02-2019 14:34:38
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10 A shortcut for run will be created in the desktop. Double click and open the “command, window”., , Run terminal, , 11 Through this command window only we have to execute the Python program because, it contains the other programming language program ie is C++. This command window, dynamically invoke the g++ compiler to compile and execute C++ program using Python, program, c:\Program Files <x86>\migw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0>echo off, Microsoft windows [Version 6.1.7601], Copyright <c> 2009 Microsoft Corporation. All rights reserved., c:\>, , 350, , Annexure III.indd 350, , 20-02-2019 14:34:39
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ANNEXURE 4, Installation of pip, First of all you need to identify whether pip is installed in your PC., If so, upgrade the pip in your system. To do this, you need to launch the, command prompt. Before trying to install or upgrade the pip, the command, will work only if you have appended the path of python directory in the, path variable of the windows., Check if pip is Installed, To check if pip is already installed in your system, navigate your command line to the, location of Python's script directory., You can install the latest version of pip from your command prompt using the following, command:, Python –m pip install –U pip, -U represents upgrading pip to the latest version., , To Check pip version:, To check the version of pip in your system, type the following command:, C:\Users\Your Name\AppData\Local\Programs\Python\Python36-32\Scripts>pip --version, The output in command prompt will look like this:, 351, , Annexure IV.indd 351, , 20-02-2019 15:49:00
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You can see the version of pip installed from the output screen., To install matplotlib, type the following in your command prompt:, Python –m pip install –U matplotlib, This command will download matplotlib from the source library. If it is already installed the, screen will look like the following:, , List Packages, To view the list of installed packages on your system, use the List command:, C:\Users\YourName\AppData\Local\Programs\Python\Python36-32\Scripts>pip list The, 352, , Annexure IV.indd 352, , 20-02-2019 15:49:00
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screen will display the list of all the packages installed on your system., , 353, , Annexure IV.indd 353, , 20-02-2019 15:49:00
