Preface
Welcome to Python!
Welcome to the wonderful world of Python! As a professional or student with working knowledge of another high-level programming language, this text was made for you in your efforts to jump straight into Python with as little overhead as possible. The goal of this book is to provide text that flows in a conversational style littered with examples to highlight your path towards Python programming.
At the time of publication, Python 2.0 was just released, so you will definitely have the latest and greatest. The supplementary CD-ROM has the three most recent versions of Python: 1.5.2, 1.6, and 2.0, not to mention the most recent release of the Java version of the Python interpreter, JPython (a.k.a. Jython).
Style: Technical, Yet Easy Reading
Rather than strictly a "beginners'" book or a pure, hard-core computer science reference book, my instructional experience indicates that an easy-to-read, yet technically-oriented book serves our purpose the best, and that is to get you up-to-speed on Python as quickly as possible, so that you can apply it to your tasks post haste. We will introduce concepts coupled with appropriate examples to expedite the learning process. At the end of each chapter you will find numerous exercises to reinforce some of the concepts and ideas acquired in your reading.
After the obligatory introduction to Python, but before heading to the core of the language, we take a "quick plunge" into Python with the "Getting Started" chapter. The intention of this chapter is for those who wish to temporarily dispense of formal reading and get their hands dirty with Python immediately. If you do not wish to travel this path, you may proceed as normal to the next set of chapters, an introduction to Python objects. Python's primitive data types, numbers, strings, lists, tuples, and dictionaries make up the next three chapters.
Python's error-handling capability is extremely useful to both the programmer and the user, and we address that topic in a separate chapter. Finally, the largest parts of the Python "core" we cover will be functions, modules, and classes... each in its own chapter. The final chapter of the text provides insight on how Python may be extended. The last section of the book is a mini-reference guide in the appendix. There we spill the beans on the core modules of the standard library, highlight the operators and built-in operators and functions for the Python types, provide solutions to selected exercises, and conclude with a small glossary of terms.
Author's Experience with Python
I discovered Python several years ago at a company called Four11. At the time, the company had one major product, the Four11.com White Page directory service. Python was being used to design the Rocketmail web-based email service that would eventually one day evolve into what is Yahoo!Mail today.
In addition to the use of C++, much of the controlling software and web front-end were done completely in Python. I participated in work done on the Yahoo!Mail address book and spellchecker. Since then, Python's appearance has spread to other Yahoo! sites, including People Search, Yellow Pages, and Maps and Driving Directions, just to name a few.
Although Python was new to me at the time, it was fairly easy to pick up; much simpler than other languages that I have learned in the past. The scarcity of the number of textbooks at the time led me to primarily use the Library Reference and Quick Reference Guide as my tools in learning, and also led to the motivation of the book you are reading right now.
Book Contents
This book is divided into two main sections. The first part, taking up about two-thirds of the text, gives you treatment of the "core" part of the language, and the second part provides a set of various advanced topics to show what you can build using Python.
Python is everywhere-sometimes it is amazing to discover who is using Python and what they are doing with it-and although we would have loved to produce additional chapters on such topics as Databases (RDBMSs, SQL, etc.), CGI Processing with HTMLgen, XML, Numerical/Scientific Processing, Visual and Graphics Image Manipulation, and Zope, there simply wasn't enough time to develop these topics into their own chapters. However, we are certainly glad that we were at least able to provide you with a good introduction to many of the key areas of Python development.
Here is a chapter-by-chapter guide:
Part I: Core Python
Chapter 1-Welcome to Python!
We begin by introducing Python to you, its history, features, benefits, etc., as well as how to obtain and install Python on your system.
Chapter 2-Getting Started
If you are an experienced programmer and just want to see "how it's done" in Python, this is the right place to go. We introduce the basic Python concepts and statements, and because many of these would be familiar to you, you would simply learn the proper syntax in Python and can get started right away on your projects without sacrificing too much reading time.
Chapter 3-Syntax and Style
This section gives you a good overview of Python's syntax as well as style hints. You will also be exposed to Python's keywords and its memory management ability. Your first Python application will be presented at the end of the chapter to give you an idea of what real Python code looks like.
Chapter 4-Python Objects
This chapter introduces Python objects. In addition to generic object attributes, we will show you all of Python's data types and operators, as well as show you different ways to categorize the standard types. Built-in functions that apply to most Python objects will also be covered.
Chapter 5-Numbers
Python has four numeric types: regular or "plain" integers, long integers, floating point real numbers, and complex numbers. You will learn about all four here, as well as the operators and built-in functions that apply to numbers.
Chapter 6-Sequences: Strings, Lists, and Tuples
Your first meaty chapter will expose you to all of Python's powerful sequence types: strings, lists, and tuples. We will show you all the built-in functions, methods, and special features, which apply to each type as well as all their operators.
Chapter 7-Dictionaries
Dictionaries are Python's mapping or hashing type. Like other data types, dictionaries also have operators and applicable built-in functions and methods.
Chapter 8-Conditionals and Loops
Like many other high-level languages, Python supports loops such as for and while, as well as if statements (and related). Python also has a built-in function called range() which enables Python's for loop to behave more like a traditional counting loop rather than the foreach iterative type loop that it is.
Chapter 9-Files and Input/Output
In addition to standard file objects and input/output, this chapter introduces you to file system access, file execution, and persistent storage.
Chapter 10-Errors and Exceptions
One of Python's most powerful constructs is its exception handling ability. You can see a full treatment of it here, instruction on how to raise or throw exceptions, and more importantly, how to create your own exception classes.
Chapter 11-Functions
Creating and calling functions are relatively straightforward, but Python has many other features that you will find useful, such as default arguments, named or keyword arguments, variable-length arguments, and some functional programming constructs. We also dip into variable scope and recursion briefly.
Chapter 12-Modules
One of Python's key strengths is in its ability to be extended. This feature allows for "plug-n-play" access as well as promotes code reuse. Applications written as modules can be imported for use by other Python modules with a single line of code. Furthermore, multiple module software distribution can be simplified by using packages.
Chapter 13-Classes and OOP
Python is a fully object-oriented programming language and was designed that way from the beginning. However, Python does not require you to program in such a manner-you may continue to develop structural/procedural code as you like, and can transition to "OO" programming anytime you are ready to take advantage of its benefits. Likewise, this chapter is here to guide you through the concepts as well as advanced topics, such as operator overloading, customization, and delegation.
Chapter 14-Execution Environment
The term "execution" can mean many different things, from callable and executable objects to running other programs (Python or otherwise). We discuss these topics in this chapter, as well as limited restricted execution and different ways of terminating execution.
Part II: Advanced Topics
Chapter 15-Regular Expressions
Regular expressions are a powerful tool used for pattern matching, extracting, and search-and-replace functionality. Learn about them here.
Chapter 16-Network Programming with Sockets
So many applications today need to be network-oriented. You have to start somewhere. In this chapter, you will learn to create clients and servers, using TCP/IP and UDP/IP.
Chapter 17-Multithreaded Programming
Multithreaded programming is a powerful way to improve the execution performance of many types of application. This chapter ends the drought of written documentation on how to do threads in Python by explaining the concepts and showing you how to correctly build a Python multithreaded application.
Chapter 18-GUI Programming with Tkinter
Based on the Tk graphical toolkit, Tkinter is Python's default GUI development module. We introduce Tkinter to you by showing you how to build simple sample GUI applications (say that 10 times, real fast!). One of the best ways to learn is to copy, and by building on top of some of these applications, you will be on your way in no time. We conclude the chapter by presenting a more complex example.
Chapter 19-Web Programming
Web programming using Python takes three main forms... Web clients, Web servers, and the popular Common Gateway Interface applications which help Web servers deliver dynamically-generated Web pages. We will cover them all in this chapter: simple and advanced Web clients and CGI applications, as well as how to build your own Web server.
Chapter 20-Extending Python
We mentioned earlier how powerful it is to have the ability to reuse code and extend the language. In pure Python, these extensions are modules, but you can also develop lower-level code in C, C++, or Java, and interface those with Python in a seamless fashion. Writing your extensions in a lower-level programming language gives you added performance and some security (because the source code does not have to be revealed). This final chapter of the book walks you step-by-step through the extension building process.
Optional Sections
Subsections or exercises marked with an asterisk ( * ) may be skipped due to their advanced or optional nature. They are usually self-contained segments that can be addressed at another time.
Those of you with enough previous programming knowledge and who have set up their Python development environments can skip the first two chapters and go straight to Chapter 2-Getting Started-where you can absorb Python into their system and be off to the races.
Book Support
I welcome any and all feedback: the good, the bad, and the ugly. If you have any comments, suggestions, kudos, complaints, bugs, questions... anything at all, feel free to contact me at cyberweb_consulting@yahoo.com.
You will find errata and other information at the book's Web site located on the Python Starship:
http://starship.python.net/crew/wesc/cpp/ 
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