Introduction to Python Programming (Computer program language)

Introduction to

Python Programming

Introduction to

Python  Programming

Gowrishankar S.

Veena A.

CRC Press

Taylor & Francis Group

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Library of Congress Cataloging‑in‑Publication Data

Names: S, Gowrishankar, author. | A, Veena author.

Title: Introduction to Python programming / Gowrishankar S, Veena A.

Description: Boca Raton : Taylor & Francis, a CRC title, part of the Taylor &

Francis imprint, a member of the Taylor & Francis Group, the academic

division of T&F Informa, plc, 2018. | Includes bibliographical references

and index.

Identifiers: LCCN 2018046894 | ISBN 9780815394372 (hardback : alk. paper) |

ISBN 9781351013239 (ebook)

Subjects: LCSH: Python (Computer program language)

Classification: LCC QA76.73.P98 S2325 2018 | DDC 005.13/3--dc23

LC record available at https://lccn.loc.gov/2018046894

Visit the Taylor & Francis Web site at

http://www.taylorandfrancis.com

and the CRC Press Web site at

http://www.crcpress.com

Dedicated to my wife Roopa K. M. and to my sister Ashwini S. Nath.

—Dr. Gowrishankar S.

I would love to dedicate this book to my parents, and my family

for their love, support and encouragement.

—Veena A.

vii

Contents

Preface........................................................................................................................................... xiii

Acknowledgment....................................................................................................................... xvii

Authors ......................................................................................................................................... xix

1. Introduction.............................................................................................................................1

1.1 What Is a Program? ....................................................................................................1

1.2 Programming Languages..........................................................................................2

1.2.1 Machine Language......................................................................................2

1.2.2 Assembly Language....................................................................................3

1.2.3 High-Level Language .................................................................................3

1.3 Software Development...............................................................................................5

1.4 History of Python Programming Language...........................................................7

1.5 Thrust Areas of Python..............................................................................................8

1.5.1 Academia......................................................................................................9

1.5.2 Scientific Tools ........................................................................................... 10

1.5.3 Machine Learning..................................................................................... 10

1.5.4 Natural Language Processing ................................................................. 10

1.5.5 Data Analysis............................................................................................. 10

1.5.6 Statistics ...................................................................................................... 11

1.5.7 Hypertext Transfer Protocol (HTTP) Library........................................ 11

1.5.8 Database Connectors/ORM/NoSQL Connectors ................................ 11

1.5.9 Web Frameworks....................................................................................... 11

1.5.10 Cloud Computing...................................................................................... 11

1.5.11 Python Distributions ................................................................................12

1.5.12 IDE Available .............................................................................................12

1.5.13 Community................................................................................................12

1.5.14 Python Stack in Industry .........................................................................12

1.6 Installing Anaconda Python Distribution ............................................................ 13

1.7 Installing PyCharm IDE to Set Up a Python Development Environment....... 16

1.8 Creating and Running Your First Python Project................................................ 19

1.9 Installing and Using Jupyter Notebook.................................................................23

1.9.1 Starting Jupyter Notebook....................................................................... 24

1.10 Open Source Software .............................................................................................27

1.10.1 Why Do People Prefer Using Open Source Software? ........................28

1.10.2 Doesn’t “Open Source” Just Mean Something Is Free of Charge?.....29

1.10.3 Open Source Licenses...............................................................................29

1.11 Summary.................................................................................................................... 32

Multiple Choice Questions................................................................................................... 32

Review Questions ..................................................................................................................34

2. Parts of Python Programming Language........................................................................35

2.1 Identifiers ...................................................................................................................35

2.2 Keywords ...................................................................................................................36

viii Contents

2.3 Statements and Expressions ....................................................................................36

2.4 Variables ..................................................................................................................... 37

2.4.1 Legal Variable Names............................................................................... 37

2.4.2 Assigning Values to Variables ................................................................. 37

2.5 Operators....................................................................................................................38

2.5.1 Arithmetic Operators................................................................................39

2.5.2 Assignment Operators..............................................................................40

2.5.3 Comparison Operators .............................................................................42

2.5.4 Logical Operators......................................................................................43

2.5.5 Bitwise Operators......................................................................................44

2.6 Precedence and Associativity .................................................................................47

2.7 Data Types..................................................................................................................48

2.7.1 Numbers .....................................................................................................48

2.7.2 Boolean .......................................................................................................48

2.7.3 Strings .........................................................................................................48

2.7.4 None ............................................................................................................49

2.8 Indentation.................................................................................................................49

2.9 Comments ..................................................................................................................50

2.9.1 Single Line Comment ...............................................................................50

2.9.2 Multiline Comments.................................................................................50

2.10 Reading Input............................................................................................................50

2.11 Print Output............................................................................................................... 51

2.11.1 str.format() Method .................................................................................... 51

2.11.2 f-strings.......................................................................................................53

2.12 Type Conversions......................................................................................................54

2.12.1 The int() Function......................................................................................54

2.12.2 The float() Function....................................................................................55

2.12.3 The str() Function ......................................................................................55

2.12.4 The chr() Function .....................................................................................56

2.12.5 The complex() Function .............................................................................56

2.12.6 The ord() Function ..................................................................................... 57

2.12.7 The hex() Function.....................................................................................57

2.12.8 The oct() Function...................................................................................... 57

2.13 The type() Function and Is Operator......................................................................58

2.14 Dynamic and Strongly Typed Language ..............................................................58

2.15 Summary....................................................................................................................59

Multiple Choice Questions...................................................................................................60

Review Questions ..................................................................................................................65

3. Control Flow Statements..................................................................................................... 67

3.1 The if Decision Control Flow Statement................................................................68

3.2 The if…else Decision Control Flow Statement.......................................................69

3.3 The if…elif…else Decision Control Statement........................................................71

3.4 Nested if Statement...................................................................................................73

3.5 The while Loop........................................................................................................... 74

3.6 The for Loop...............................................................................................................79

3.7 The continue and break Statements .......................................................................... 81

Contents ix

3.8 Catching Exceptions Using try and except Statement..........................................84

3.8.1 Syntax Errors..............................................................................................84

3.8.2 Exceptions ..................................................................................................84

3.8.3 Exception Handling Using try…except…finally.....................................85

3.9 Summary....................................................................................................................89

Multiple Choice Questions...................................................................................................90

Review Questions ..................................................................................................................93

4. Functions ................................................................................................................................95

4.1 Built-In Functions .....................................................................................................95

4.2 Commonly Used Modules.......................................................................................97

4.3 Function Definition and Calling the Function.....................................................99

4.4 The return Statement and void Function.............................................................. 103

4.5 Scope and Lifetime of Variables ........................................................................... 106

4.6 Default Parameters ................................................................................................. 108

4.7 Keyword Arguments.............................................................................................. 109

4.8 *args and **kwargs.................................................................................................. 110

4.9 Command Line Arguments .................................................................................. 112

4.10 Summary.................................................................................................................. 113

Multiple Choice Questions................................................................................................. 113

Review Questions ................................................................................................................ 117

5. Strings................................................................................................................................... 119

5.1 Creating and Storing Strings................................................................................. 119

5.1.1 The str() Function .................................................................................... 120

5.2 Basic String Operations.......................................................................................... 120

5.2.1 String Comparison..................................................................................122

5.2.2 Built-In Functions Used on Strings ......................................................122

5.3 Accessing Characters in String by Index Number.............................................123

5.4 String Slicing and Joining...................................................................................... 124

5.4.1 Specifying Steps in Slice Operation...................................................... 126

5.4.2 Joining Strings Using join() Method..................................................... 127

5.4.3 Split Strings Using split() Method......................................................... 127

5.4.4 Strings Are Immutable ........................................................................... 128

5.4.5 String Traversing..................................................................................... 128

5.5 String Methods........................................................................................................ 131

5.6 Formatting Strings.................................................................................................. 138

5.6.1 Format Specifiers..................................................................................... 140

5.6.2 Escape Sequences .................................................................................... 141

5.6.3 Raw Strings .............................................................................................. 142

5.6.4 Unicodes ................................................................................................... 142

5.7 Summary.................................................................................................................. 143

Multiple Choice Questions................................................................................................. 143

Review Questions ................................................................................................................ 146

6. Lists........................................................................................................................................ 149

6.1 Creating Lists........................................................................................................... 149

6.2 Basic List Operations.............................................................................................. 151

6.2.1 The list() Function.................................................................................... 151

x Contents

6.3 Indexing and Slicing in Lists................................................................................. 152

6.3.1 Modifying Items in Lists........................................................................ 153

6.4 Built-In Functions Used on Lists .......................................................................... 155

6.5 List Methods ............................................................................................................ 156

6.5.1 Populating Lists with Items................................................................... 158

6.5.2 Traversing of Lists ................................................................................... 159

6.5.3 Nested Lists.............................................................................................. 167

6.6 The del Statement .................................................................................................... 169

6.7 Summary.................................................................................................................. 170

Multiple-Choice Questions................................................................................................. 170

Review Questions ................................................................................................................ 173

7. Dictionaries.......................................................................................................................... 175

7.1 Creating Dictionary................................................................................................ 175

7.2 Accessing and Modifying key:value Pairs in Dictionaries................................. 178

7.2.1 The dict() Function................................................................................... 179

7.3 Built-In Functions Used on Dictionaries ............................................................. 179

7.4 Dictionary Methods................................................................................................ 181

7.4.1 Populating Dictionaries with key:value Pairs....................................... 183

7.4.2 Traversing of Dictionary ........................................................................ 185

7.5 The del Statement .................................................................................................... 193

7.6 Summary.................................................................................................................. 193

Multiple Choice Questions................................................................................................. 193

Review Questions ................................................................................................................ 198

8. Tuples and Sets.................................................................................................................... 201

8.1 Creating Tuples ....................................................................................................... 201

8.2 Basic Tuple Operations...........................................................................................203

8.2.1 The tuple() Function ................................................................................204

8.3 Indexing and Slicing in Tuples .............................................................................205

8.4 Built-In Functions Used on Tuples ....................................................................... 207

8.5 Relation between Tuples and Lists .......................................................................208

8.6 Relation between Tuples and Dictionaries..........................................................209

8.7 Tuple Methods......................................................................................................... 210

8.7.1 Tuple Packing and Unpacking .............................................................. 211

8.7.2 Traversing of Tuples ................................................................................ 211

8.7.3 Populating Tuples with Items................................................................ 212

8.8 Using zip() Function................................................................................................ 216

8.9 Sets ............................................................................................................................ 216

8.10 Set Methods ............................................................................................................. 218

8.10.1 Traversing of Sets .................................................................................... 219

8.11 Frozenset.................................................................................................................. 221

8.12 Summary..................................................................................................................222

Multiple Choice Questions.................................................................................................222

Review Questions ................................................................................................................227

Contents xi

9. Files........................................................................................................................................229

9.1 Types of Files ...........................................................................................................230

9.1.1 File Paths................................................................................................... 231

9.1.2 Fully Qualified Path and Relative Path................................................ 232

9.2 Creating and Reading Text Data...........................................................................233

9.2.1 Creating and Opening Text Files ..........................................................233

9.2.2 File close() Method...................................................................................235

9.2.3 Use of with Statements to Open and Close Files................................. 237

9.2.4 File Object Attributes.............................................................................. 239

9.3 File Methods to Read and Write Data.................................................................. 239

9.4 Reading and Writing Binary Files........................................................................ 247

9.5 The Pickle Module .................................................................................................. 249

9.6 Reading and Writing CSV Files ............................................................................ 251

9.7 Python os and os.path Modules ........................................................................... 257

9.8 Summary.................................................................................................................. 261

Multiple Choice Questions................................................................................................. 262

Review Questions ................................................................................................................265

10. Regular Expression Operations....................................................................................... 267

10.1 Using Special Characters ....................................................................................... 267

10.1.1 Using r Prefix for Regular Expressions................................................272

10.1.2 Using Parentheses in Regular Expressions .........................................272

10.2 Regular Expression Methods ................................................................................ 273

10.2.1 Compiling Regular Expressions Using compile() Method of

re Module.................................................................................................. 273

10.2.2 Match Objects .......................................................................................... 274

10.3 Named Groups in Python Regular Expressions ................................................ 282

10.4 Regular Expression with glob Module ................................................................. 282

10.5 Summary..................................................................................................................284

Multiple Choice Questions.................................................................................................284

Review Questions ................................................................................................................ 287

11. Object-Oriented Programming .......................................................................................289

11.1 Classes and Objects ................................................................................................289

11.2 Creating Classes in Python ................................................................................... 291

11.3 Creating Objects in Python ................................................................................... 293

11.4 The Constructor Method ....................................................................................... 294

11.5 Classes with Multiple Objects............................................................................... 297

11.5.1 Using Objects as Arguments ................................................................. 301

11.5.2 Objects as Return Values........................................................................303

11.6 Class Attributes versus Data Attributes..............................................................306

11.7 Encapsulation ..........................................................................................................307

11.7.1 Using Private Instance Variables and Methods ..................................309

11.8 Inheritance ............................................................................................................... 311

11.8.1 Accessing the Inherited Variables and Methods ................................ 312

11.8.2 Using super() Function and Overriding Base Class Methods........... 314

xii Contents

11.8.3 Multiple Inheritances.............................................................................. 317

11.8.4 Method Resolution Order (MRO) ......................................................... 320

11.9 The Polymorphism ................................................................................................. 328

11.9.1 Operator Overloading and Magic Methods........................................ 331

11.10 Summary..................................................................................................................335

Multiple Choice Questions.................................................................................................336

Review Questions ................................................................................................................338

12. Introduction to Data Science............................................................................................341

12.1 Functional Programming ......................................................................................341

12.1.1 Lambda..................................................................................................... 341

12.1.2 Iterators .....................................................................................................342

12.1.3 Generators ................................................................................................343

12.1.4 List Comprehensions ..............................................................................344

12.2 JSON and XML in Python .....................................................................................346

12.2.1 Using JSON with Python .......................................................................347

12.2.2 Using Requests Module..........................................................................353

12.2.3 Using XML with Python ........................................................................355

12.2.4 JSON versus XML ................................................................................... 359

12.3 NumPy with Python ..............................................................................................359

12.3.1 NumPy Arrays Creation Using array() Function................................360

12.3.2 Array Attributes ...................................................................................... 361

12.3.3 NumPy Arrays Creation with Initial Placeholder Content............... 362

12.3.4 Integer Indexing, Array Indexing, Boolean Array

Indexing, Slicing and Iterating in Arrays ............................................364

12.3.5 Basic Arithmetic Operations on NumPy Arrays................................ 367

12.3.6 Mathematical Functions in NumPy .....................................................368

12.3.7 Changing the Shape of an Array .......................................................... 369

12.3.8 Stacking and Splitting of Arrays........................................................... 370

12.3.9 Broadcasting in Arrays........................................................................... 371

12.4 Pandas ....................................................................................................................... 374

12.4.1 Pandas Series ........................................................................................... 375

12.4.2 Pandas DataFrame ..................................................................................380

12.5 Altair......................................................................................................................... 398

12.6 Summary..................................................................................................................409

Multiple Choice Questions................................................................................................. 410

Review Questions ................................................................................................................ 413

Appendix-A: Debugging Python Code ................................................................................. 415

Bibliography................................................................................................................................425

Solutions ......................................................................................................................................427

Index .............................................................................................................................................437

xiii

Preface

This book presents an intuitive approach to the concepts of Python Programming for

students. It is appropriate for courses generally known as “Introduction to Python

Programming.” We have tried to write a book that assists students in discovering the

power of Python programming. We have taken into account the reality that students taking

“Introduction to Python Programming” course are likely to come from a variety of dis￾ciplines. In addition to Computer Science majors, there tend to be students from other

majors like other engineering streams, physics, chemistry, biology, environmental science,

geography, economics, psychology and business.

This book differs from traditional texts not only in its philosophy but also in its overall

focus, level of activities, development of topics, and attention to programming details. The

emphasis is on understanding Python programming concepts. Reading a programming

book is different from reading a newspaper or a novel. Don’t be discouraged if you have

to read a passage more than once in order to understand it. We recommend that you keep

this book for reference purposes after you finish working through the course. Because

you will likely forget some of the specific details of Python programming language, the

book will serve as a useful reminder. Students will appreciate the many programming

examples within the text. Programs are carefully selected to bring the theoretical concepts

to fruition. Our aim is to get the reader to productivity as quickly as possible without sac￾rificing the overall flow quality.

In fact, if you are a novice programmer, with some dedication and hard work you should

be able to learn Python Programming as your first programming language. As we intro￾duce each new feature of the language, we usually provide a complete program as an

example to illustrate the feature. Just as a picture is worth a thousand words, so is a prop￾erly chosen programming example. We present the material in a way to encourage student

thinking and we show students how to generalize key concepts once they are introduced,

which can be used to solve real-world problems. Programming questions that accompany

the end of each chapter are based on worked examples which help students to gain solid

knowledge of the basics and assess their own level of understanding before moving on.

Students are highly encouraged to solve these programs to gain a solid hold on Python

programming language.

This book takes you through step by step process of learning the Python programming

language. Each line of the code is marked with numbers and is explained in detail. In this

book all the names of variables, strings, lists, dictionaries, tuples, functions, methods and

classes consist of several natural words and in the explanation part they are written in

italics to indicate the readers that they are part of programming code and to distinguish

them from normal words. This programming style of using readable natural names makes

the reading of code lot easier and prevents programming errors. Learning outcome com￾ponent is mentioned at the beginning of each chapter that calls the attention of the readers

to important items in the chapter. A summary of important concepts appears at the end

of each chapter.

We hope that students using the book will come away with an appreciation of the beauty,

power, and tremendous utility of Python programming language and that they will have

fun along the way.

xiv Preface

Organization of Chapters

Here’s a brief rundown of what you will find in each chapter:

In Chapter 1, the advantages of using Python programming language is discussed

and the scope of Python’s reach, and all the different areas of application develop￾ment in which Python plays a part is identified. This chapter also covers the down￾loading and installation of Anaconda distribution and PyCharm IDE. You will be

guided towards setting up your own Python development environment. You will

understand the meaning of Open Source Software and its various licenses.

In Chapter 2, you will learn the basic building blocks of Python programming lan￾guage like arithmetic operators, data types, operator precedence and associativ￾ity and construct complex expressions using operators. This chapter teaches you

the syntax of Python language which you need to know before writing Python

programs.

In Chapter 3, Python statements such as if, if…else, if…elif…else are taught which are

used to transfer the control from one part of the program to another. Loops to run

one or more statements repeatedly are examined. Controlling the flow of execu￾tion is carried out through the break and continue statements. To take advantage

of the iterative capabilities in a computer, you need to know how to include loops

and conditional logic within your program. How to deal with errors in the input

is also part of this chapter.

In Chapter 4, you will determine how to create functions, pass values to and return

values from the function. In this chapter, commonly used modules and built-in

functions are identified. This chapter also includes discussion on different func￾tion features like keyword arguments and variable number of arguments. You’ll

learn how to use functions to make your code more efficient and flexible.

In Chapter 5, some of the more commonly occurring string tasks, such as concat￾enating strings, trimming of white spaces, splitting string as well as finding sub￾strings within strings is covered. Various string methods to manipulate strings are

described in detail. Indexing, slicing and joining of strings are illustrated through

figures. Formatting of the string using f-strings is also outlined.

In Chapter 6, one of the main pillars of Python programming language and the built￾in data type, Lists, is discussed which acts as a container to hold items of differ￾ent types. Creating, slicing and indexing of lists is elaborated with high-grade

examples. Use of list methods in manipulating Python programs is demonstrated.

In Chapter 7, another built-in data type in Python programming language, Dictionary,

is covered in depth. Accessing and modifying the key:value pairs of Dictionaries

is demonstrated.

In Chapter 8, role of tuples in returning multiple values from functions and storing

heterogeneous elements of fixed sized is discussed. Mathematical operations like

union and intersection are demonstrated using sets. Different methods supported

by tuples and sets are identified.

In Chapter 9, you will deal with file-based input and output functions, including

how to load files, perform basic operations, and save the results back to disk.