Python Standard Library

Python Standard Library, an essential guide for serious Python programmers, delivers accurate, author-tested documentation of all the modules in the Python Standard Library, along with over 300 annotated example scripts using the modules. This version of the book covers all the new modules and related information for Python 2.0, the first major release of Python in four years.

Preface

"We'd like to pretend that 'Fredrik' is a role, but even hundreds of volunteers couldn't possibly keep up. No,'Fredrik' is the result of crossing an http server with a spam filter with an emacs whatsit and some other stuff besides."

—Gordon McMillan, June 1998

The Python 2.0 distribution comes with an extensive standard library, comprised of over 200 modules. This book briefly describes each module and provides one or more sample scripts showing how to use it. All in all, this book contains 360 sample scripts.

About This Book

"Those people who have nothing better to do than post on the Internet all day long are rarely the ones who have the most insights."

—Jakob Nielsen, December 1998

Since I first stumbled upon Python some five years ago, I've spent hundreds of hours answering questions on the comp.lang.python newsgroup. Maybe someone found a module that might be exactly what he wanted, but he couldn't really figure out how to use it. Maybe someone had picked the wrong module for the task. Or maybe someone tried to reinvent the wheel. Often, a short sample script could be much more helpful than a pointer to the reference documentation.

After posting a couple of scripts each week, for a number of years, you end up with a rather large collection of potentially useful scripts. What you'll find in this book are the best parts from over 3,000 newsgroup messages. You'll also find hundreds of new scripts added to make sure every little nook and cranny of standard library has been fully covered.

I've worked hard to make the scripts both understandable and adaptable. I've intentionally kept the annotations as short as possible. If you want more background, there's plenty of reference material shipped with most Python distributions. In this book, the emphasis is on the code.

What About Tkinter?

This book covers the entire standard library, except the (optional) Tkinter user-interface library. There are several reasons for this, mostly related to time, space, and the fact that I'm working on several other Tkinter documentation projects.

Production Details

This book was written in DocBook SGML. I used a variety of tools, including Secret Labs' PythonWorks, Excosoft Documentor, James Clark's Jade DSSSL processor, Norm Walsh's DocBook stylesheets, and a bunch of Python scripts, of course.

Thanks to my referees: Tim Peters, Guido van Rossum, David Ascher, Mark Lutz, and Rael Dornfest, and the PythonWare crew: Matthew Ellis, Håkan Karlsson, and Rune Uhlin.

About the Examples

Unless otherwise noted, all examples run under Python 1.5.2 and Python 2.0. I've tried not to depend on internal details, and I expect most scripts to work with upcoming 2.x versions as well.

The examples have been tested on Windows, Solaris, and Linux. Except for a few scripts that depend on platform-specific modules, the examples should work right out of the box on most other platforms as well. (If you find something that doesn't work as expected, let me know!)

All code is copyrighted. Of course, you're free to use one or more modules in your own programs, just don't forget where you got them.

Most script files are named after the module they're using, followed by the string "-example-" and a unique "serial number." Note that the scripts sometimes appear out of order; it's done this way on purpose, to match the filenames used in an earlier version of this book, (the eff-bot guide to) The Standard Python Library.

Chapter 1. Core Modules

"Since the functions in the C runtime library are not part of the Win32 API, we believe the number of applications that will be affected by this bug to be very limited."

—Microsoft, January 1999

1.1 Introduction

Python's standard library covers a wide range of modules. It includes everything from modules that are as much apart of the Python language as the types and statements defined by the language specification, to obscure modules that are probably useful only to a small number of programs.

This chapter describes a number of fundamental standard library modules. Any larger Python program is likely to use most of these modules, either directly or indirectly.

1.1.1 Built-in Functions and Exceptions

The following two modules are even more basic than all other modules combined: the _ _builtin_ _ module, which defines built-in functions (like len, int, and range), and the exceptions module, which defines all built-in exceptions.

Python imports both modules when it starts up, and makes their content available for all programs.

1.1.2 Operating System Interface Modules

There are a number of modules modeled after the POSIX standard API and the standard C library that provide platform-independent interfaces to the underlying operating system.

The modules in this group include os, which provides file and process operations, os.path, which offers a platform-independent way to pull apart and put together filenames, and time, which provides functions to work with dates and times.

To some extent, networking and thread support modules could also belong in this group, but they are not supported by all Python implementations.

1.1.3 Type Support Modules

Several built-in types have support modules in the standard library. The string module implements commonly used string operations, the math module provides math operations and constants, and the cmath module does the same for complex numbers.

1.1.4 Regular Expressions

The re module provides regular expressions support for Python. Regular expressions are string patterns written in a special syntax, which can be used to match strings and extract substrings.

1.1.5 Language Support Modules

sys gives you access to various interpreter variables, such as the module search path, and the interpreter version. operator provides functional equivalents to many built-in operators. copy allows you to copy objects. And finally, gcgives you more control over the garbage collector facilities in Python 2.0.

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