Python Distilled / Edition 1

by David Beazley

Overview

Expert insight for modern Python (3.6+) coding from the author of Python Essential Reference

Python educator Dave Beazley’s concise handbook focuses on the essential core of the Python programming language, with code examples to illuminate how Python works and how to structure programs that can be more easily explained, tested, and debugged. Rather than trying to cover every possible feature and quirk of a 30-year-old language, this pragmatic guide provides a concise narrative related to fundamental programming topics that form the foundation for Python projects of any size including

• Data abstraction
• Control flow
• Program structure
• Functions: master functions and functional programming idioms
• Objects: control objects and master the "protocols" that define their behavior
• Modules: plan for project growth by understanding modules and packages
• Generators
• Classes: understand classes from both high-level and technical perspectives
• I/O handling: proper techniques and abstractions
• Dicts

"This is a pragmatic book that presents some of the most important topics about the Python programming language in a concise form, designed to make it easier to find out the most relevant information bits in a context where resources abound and frequently are just too overwhelming."

—Victor Domingos, Software Developer, Slim Business Solutions, The No Title® Tech Blog

Product Details

ISBN-13:	9780134173276
Publisher:	Pearson Education
Publication date:	09/22/2021
Series:	Developer's Library
Edition description:	5th ed.
Pages:	352
Sales rank:	424,465
Product dimensions:	6.90(w) x 9.00(h) x 0.80(d)

About the Author

David Beazley is the author of the Python Essential Reference, Fourth Edition (Addison-Wesley), and Python Cookbook, Third Edition (O'Reilly Media). He currently teaches advanced computer science courses through his company, Dabeaz LLC (www.dabeaz.com). He's been using, writing about, speaking about, and teaching Python since 1996.

Read an Excerpt

IntroductionIntroduction

THIS BOOK IS INTENDED TO BE A CONCISE REFERENCE to the Python programming language. Although an experienced programmer will probably be able to learn Python from this book, it's not intended to be an extended tutorial or a treatise on how to program. Rather, the goal is to present the core Python language, the contents of the Python library, and the Python extension API in a manner that's accurate and concise. This book assumes that the reader has prior programming experience with Python or another language such as C or Java. In a addition, a general familiarity with systems programming topics (for example, basic operating system concepts and network programming) may be useful in understanding certain parts of the library reference.

Python is freely available for download at http://www.python.org. Versions are available for almost every operating system, including UNIX, Windows, Macintosh, and Java. In addition, the Python website includes links to documentation, how-to guides, and a wide assortment of third-party software.

The contents of this book are based on Python 2.4. However, readers should be aware that Python is a constantly evolving language. Most of the topics described herein are likely to be applicable to future versions of Python 2.x. In addition, much of the material is applicable to earlier releases. To a lesser extent, the topics in this book also apply to alternative Python implementations such as Jython (an implementation of Python in Java) and IronPython (an implementation of Python for .NET). However, those implementations are not the primary focus.

Just as Python is an evolving language, the third edition ofPython Essential Reference has evolved to make use of new language features and new library modules. In fact, since the publication of the second edition, Python has undergone a dramatic transformation involving significant changes to core parts of the language. In addition, a wide variety of new and interesting features have been added. Rather than discussing these changes as a mere afterthought, the entire text has been updated to reflect the modern state of Python programming. Although no distinction is given to new features, detailed descriptions of language changes can be found at http://www.python.org.

Finally, it should be noted that Python already includes thousands of pages of useful documentation. The contents of this book are largely based on that documentation, but with a number of key differences. First, this reference presents most of the same information in a much more compact form, with different examples, and alternative descriptions of many topics. Second, a significant number of topics in the library reference have been expanded to include outside reference material. This is especially true for low-level system and networking modules in which effective use of a module normally relies on a myriad of options listed in manuals and outside references. In addition, in order to produce a more concise reference, a number of deprecated and relatively obscure library modules have been omitted. Finally, this reference doesn't attempt to cover large frameworks such as Tkinter,

In writing this book, it has been my goal to produce a reference containing virtually everything I have needed to use Python and its large collection of modules. Although this is by no means a gentle introduction to the Python language, I hope that you find the contents of this book to be a useful addition to your programming reference library for many years to come. I welcome your comments.

David Beazley
Chicago, Illinois
November 27, 2005

© Copyright Pearson Education. All rights reserved.

Table of Contents

Preface xiii
Chapter 1: Python Basics 1
1.1 Running Python 1
1.2 Python Programs 2
1.3 Primitives, Variables, and Expressions 3
1.4 Arithmetic Operators 5
1.5 Conditionals and Control Flow 7
1.6 Text Strings 9
1.7 File Input and Output 12
1.8 Lists 13
1.9 Tuples 15
1.10 Sets 17
1.11 Dictionaries 18
1.12 Iteration and Looping 21
1.13 Functions 22
1.14 Exceptions 24
1.15 Program Termination 26
1.16 Objects and Classes 26
1.17 Modules 30
1.18 Script Writing 32
1.19 Packages 33
1.20 Structuring an Application 34
1.21 Managing Third-Party Packages 35
1.22 Python: It Fits Your Brain 36
Chapter 2: Operators, Expressions, and Data Manipulation 37
2.1 Literals 37
2.2 Expressions and Locations 38
2.3 Standard Operators 39
2.4 In-Place Assignment 41
2.5 Object Comparison 42
2.6 Ordered Comparison Operators 42
2.7 Boolean Expressions and Truth Values 43
2.8 Conditional Expressions 44
2.9 Operations Involving Iterables 45
2.10 Operations on Sequences 47
2.11 Operations on Mutable Sequences 49
2.12 Operations on Sets 50
2.13 Operations on Mappings 51
2.14 List, Set, and Dictionary Comprehensions 52
2.15 Generator Expressions 54
2.16 The Attribute (.) Operator 56
2.17 The Function Call () Operator 56
2.18 Order of Evaluation 56
2.19 Final Words: The Secret Life of Data 58
Chapter 3: Program Structure and Control Flow 59
3.1 Program Structure and Execution 59
3.2 Conditional Execution 59
3.3 Loops and Iteration 60
3.4 Exceptions 64
3.5 Context Managers and the with Statement 75
3.6 Assertions and __debug__ 77
3.7 Final Words 78
Chapter 4: Objects, Types, and Protocols 79
4.1 Essential Concepts 79
4.2 Object Identity and Type 80
4.3 Reference Counting and Garbage Collection 81
4.4 References and Copies 83
4.5 Object Representation and Printing 84
4.6 First-Class Objects 85
4.7 Using None for Optional or Missing Data 87
4.8 Object Protocols and Data Abstraction 87
4.9 Object Protocol 89
4.10 Number Protocol 90
4.11 Comparison Protocol 92
4.12 Conversion Protocols 94
4.13 Container Protocol 95
4.14 Iteration Protocol 97
4.15 Attribute Protocol 98
4.16 Function Protocol 98
4.17 Context Manager Protocol 99
4.18 Final Words: On Being Pythonic 99
Chapter 5: Functions 101
5.1 Function Definitions 101
5.2 Default Arguments 101
5.3 Variadic Arguments 102
5.4 Keyword Arguments 103
5.5 Variadic Keyword Arguments 104
5.6 Functions Accepting All Inputs 104
5.7 Positional-Only Arguments 105
5.8 Names, Documentation Strings, and Type Hints 106
5.9 Function Application and Parameter Passing 107
5.10 Return Values 109
5.11 Error Handling 110
5.12 Scoping Rules 111
5.13 Recursion 114
5.14 The lambda Expression 114
5.15 Higher-Order Functions 115
5.16 Argument Passing in Callback Functions 118
5.17 Returning Results from Callbacks 121
5.18 Decorators 124
5.19 Map, Filter, and Reduce 127
5.20 Function Introspection, Attributes, and Signatures 129
5.21 Environment Inspection 131
5.22 Dynamic Code Execution and Creation 133
5.23 Asynchronous Functions and await 135
5.24 Final Words: Thoughts on Functions and Composition 137
Chapter 6: Generators 139
6.1 Generators and yield 139
6.2 Restartable Generators 142
6.3 Generator Delegation 142
6.4 Using Generators in Practice 144
6.5 Enhanced Generators and yield Expressions 146
6.6 Applications of Enhanced Generators 148
6.7 Generators and the Bridge to Awaiting 151
6.8 Final Words: A Brief History of Generators and Looking Forward 152
Chapter 7: Classes and Object-Oriented Programming 153
7.1 Objects 153
7.2 The class Statement 154
7.3 Instances 155
7.4 Attribute Access 156
7.5 Scoping Rules 158
7.6 Operator Overloading and Protocols 159
7.7 Inheritance 160
7.8 Avoiding Inheritance via Composition 163
7.9 Avoiding Inheritance via Functions 166
7.10 Dynamic Binding and Duck Typing 167
7.11 The Danger of Inheriting from Built-in Types 167
7.12 Class Variables and Methods 169
7.13 Static Methods 173
7.14 A Word about Design Patterns 176
7.15 Data Encapsulation and Private Attributes 176
7.16 Type Hinting 179
7.17 Properties 180
7.18 Types, Interfaces, and Abstract Base Classes 183
7.19 Multiple Inheritance, Interfaces, and Mixins 187
7.20 Type-Based Dispatch 193
7.21 Class Decorators 194
7.22 Supervised Inheritance 197
7.23 The Object Life Cycle and Memory Management 199
7.24 Weak References 204
7.25 Internal Object Representation and Attribute Binding 206
7.26 Proxies, Wrappers, and Delegation 208
7.27 Reducing Memory Use with __slots__ 210
7.28 Descriptors 211
7.29 Class Definition Process 215
7.30 Dynamic Class Creation 216
7.31 Metaclasses 217
7.32 Built-in Objects for Instances and Classes 222
7.33 Final Words: Keep It Simple 223
Chapter 8: Modules and Packages 225
8.1 Modules and the import Statement 225
8.2 Module Caching 227
8.3 Importing Selected Names from a Module 228
8.4 Circular Imports 230
8.5 Module Reloading and Unloading 232
8.6 Module Compilation 233
8.7 The Module Search Path 234
8.8 Execution as the Main Program 234
8.9 Packages 235
8.10 Imports Within a Package 237
8.11 Running a Package Submodule as a Script 238
8.12 Controlling the Package Namespace 239
8.13 Controlling Package Exports 240
8.14 Package Data 241
8.15 Module Objects 242
8.16 Deploying Python Packages 243
8.17 The Penultimate Word: Start with a Package 244
8.18 The Final Word: Keep It Simple 245
Chapter 9: Input and Output 247
9.1 Data Representation 247
9.2 Text Encoding and Decoding 248
9.3 Text and Byte Formatting 250
9.4 Reading Command-Line Options 254
9.5 Environment Variables 256
9.6 Files and File Objects 256
9.7 I/O Abstraction Layers 260
9.8 Standard Input, Output, and Error 263
9.9 Directories 264
9.10 The print() function 265
9.11 Generating Output 265
9.12 Consuming Input 266
9.13 Object Serialization 268
9.14 Blocking Operations and Concurrency 269
9.15 Standard Library Modules 273
9.16 Final Words 296
Chapter 10: Built-in Functions and Standard Library 297
10.1 Built-in Functions 297
10.2 Built-in Exceptions 314
10.3 Standard Library 318
10.4 Final Words: Use the Built-Ins 320
Index 321

Foreword

As Python's creator, I'm really happy that this book has appeared. It marks a point in time when Python is becoming a mainstream language, with a rapidly growing community of users. If you consider yourself an (established or aspiring) member of this community, you need neither evangelizing nor proselytizing, and you already know Python well enough to have chosen it as an essential element of your personal toolbox.

This book aims to be your guide on the rest of your journey through the Python world. It documents every detail of the language's syntax and semantics, provides reference documentation and examples for most standard library modules, and even contains a quick reference for writing extension modules. All this information is thoroughly indexed and cross-referenced, and where necessary contains pointers to additional online documentation for obscure details.

You might think that all this information is already available for free on the Python Web site (www.python.org). Sure, it's all there-in fact, I'm certain that the author, my good friend David Beazley, consulted the Web site many times. He would have been a fool not to!

However, with all due respect for the authors of Python's online documentation (myself included!), this book has a huge advantage over the Web site: You can easily take it with you on a trip into the desert. Seriously, David has reorganized and rewritten all the information for maximum clarity, pulled things together from different sources, removed redundancies, clarified ambiguities, added better examples, and so on. He also had a benefit that few readers of the Web site have: direct access to my brain! This summer, David spent a few weeksvisiting CNRI, the research lab in Reston that Python calls home. During this time we had many interesting and fruitful discussions about Python, this book, the meaning of life, southwestern cooking, the joys and pains of teaching computer science to noncomputer scientists, and the Spanish Inquisition. (Remember? Nobody expects the Spanish Inquisition!)

I hope that you will enjoy using this book, and that it will serve you well. I also hope that you will continue to enjoy using Python, and that it will serve you well. Python is a great programming language, and I would like to use this opportunity to thank the entire Python community for making Python what it is today. Without the thousands of believers, users, contributors, entrepreneurs, and developers who make up the Python community, my own energy directed toward Python would have dried up long ago. I see this as the essence of open source projects: The energy and creativity of many people with diverse goals together can work miracles!

-Guido van Rossum
Baltimore, MD
9/13/1999