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 succinct. This book assumes that the reader has prior programming experience with Python or other languages such as C or Java. In addition, a general familiarity with systems programming topics (for example, basic operating system concepts, process management, and network programming) may be useful in understanding certain parts of the library reference.

Python is freely available for download at r,ttp://www.python.org.Versions are available for UNIX, Windows, Macintosh, and Java. In addition, this site includes links to documentation, how-to guides, and a wide assortment of extension modules.

What's Inside?

The contents of this book are based on Python 2.1. However, readers shoed 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, most topics are applicable to earlier releases. To a lesser extent, the topics in this book also apply to JPython, an implementation of Python entirely in Java. However, that is not the primary focus of this book.

It should be noted that just as Python is an evolving language, the Second Edition of Python Essential Reference has evolved to make use of new language features and new library modules added in Python 2.1. Rather than merely describing new language features as an afterthought, recently added features have been freely used and incorporated throughout the text. Although no distinction is given to new additions, detailed descriptions of language changes can easily be found online.

Finally, note that Python is distributed with hundreds of pages of reference documentation. The contents of this book are largely based on that documentation, but with a number of enhancements, additions, and omissions. First, this reference presents most of the same material in a 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 additional outside reference material. This is especially true for lowlevel system and networking modules in which effective use of a module normally relies on a myriad of options listed in UNIX manual pages and outside reference material. 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, XML, or the COM extensions, as these topics are beyond the scope of this book and are described in books of their own.

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, IL
6/1/2001