OReilly Media. - Learning Python

• Covers both Python 3.0 and Python 2.6it emphasizes 3.0, but notes differences in 2.6
• Includes a set of new chapters mainly targeted at advanced core-language topics
• Reorganizes some existing material and expands it with new examples for clarity

To address this dichotomy and to meet the needs of all potential readers, this edition of this book has been updated to cover both Python 3.0 and Python 2.6 (and later releases in the 3.X and 2.X lines). Its intended for programmers using Python 2, programmers using Python 3, and programmers stuck somewhere between the two.

That is, you can use this book to learn either Python line. Although the focus here is on 3.0 primarily, 2.6 differences and tools are also noted along the way for programmers using older code. While the two versions are largely the same, they diverge in some important ways, and Ill point these out along the way.

For instance, Ill use 3.0 print calls in most examples, but will describe the 2.6 print statement, too, so you can make sense of earlier code. Ill also freely introduce new features, such as the nonlocal statement in 3.0 and the string format method in 2.6 and 3.0, and will point out when such extensions are not present in older Pythons.

If you are learning Python for the first time and dont need to use any legacy code, I encourage you to begin with Python 3.0; it cleans up some longstanding warts in the language, while retaining all the original core ideas and adding some nice new tools. Many popular Python libraries and tools will likely be available for Python 3.0 by the time you read these words, especially given the file I/O performance improvements expected in the upcoming 3.1 release. If you are using a system based on Python 2.X, however, youll find that this book addresses your concerns, too, and will help you migrate to 3.0 in the future.

By proxy, this edition addresses other Python version 2 and 3 releases as well, though some older version 2.X code may not be able to run all the examples here. Although class decorators are available in both Python 2.6 and 3.0, for example, you cannot use them in an older Python 2.X that did not yet have this feature. See Tables later in this Preface for summaries of 2.6 and 3.0 changes.