Here it is—a shiny new edition of Beginning Python. If you count its predecessor, Practical Python, this is actually the third edition, and a book I’ve been involved with for the better part of a decade. During this time, Python has seen many interesting changes, and I’ve done my best to update my introduction to the language. At the moment, Python is facing perhaps its most marked transition in a very long time: the introduction of version 3. As I write this, the final release isn’t out yet, but the features are clearly defined and working versions are available. One interesting challenge linked to this language revision is that it isn’t backward-compatible. In other words, it doesn’t simply add features that I could pick and choose from in my writing. It also changes the existing language, so that certain things that are true for Python 2.5 no longer hold.

Had it been clear that the entire Python community would instantly switch to the new version and update all its legacy code, this would hardly be a problem. Simply describe the new language! However, a lot of code written for older versions exists, and much will probably still be written, until version 3 is universally accepted as The Way To Go™.

So, how have I gotten myself out of this pickle? First of all, even though there are incompatible changes, most of the language remains the same. Therefore, if I wrote entirely about Python 2.5, it would be mostly correct for Python 3 (and even more so for its companion release, 2.6). As for the parts that will no longer be correct, I have been a bit conservative and assumed that full adoption of version 3 will take some time. I have based the book primarily on 2.5, and noted things that will change throughout the text. In addition, I’ve included Appendix D, which gives you an overview of the main changes. I think this will work out for most readers.

In writing this second edition, I have had a lot of help from several people. Just as with the previous two versions (the first edition, and, before it, Practical Python), Jason Gilmore got me started and played an important role in getting the project on the road. As it has moved along, Richard Dal Porto, Frank Pohlmann, and Dominic Shakeshaft have been instrumental in keeping it going. Richard Taylor has certainly played a crucial role in ensuring that the code is correct (and if it still isn’t, I’m the one to blame), and Marilyn Smith has done a great job tuning my writing. My thanks also go out to other Apress staff, including Liz Berry, Beth Christmas, Steve Anglin, and Tina Nielsen, as well as various readers who have provided errata and helpful suggestions, including Bob Helmbold and Waclaw Kusnierczyk. I am also, of course, still thankful to all those who helped in getting the first two incarnations of this book on the shelves.

Preface to the First Edition

A few years ago, Jason Gilmore approached me about writing a book for Apress. He had read my online Python tutorials and wanted me to write a book in a similar style. I was flattered, excited, and just a little nervous. The one thing that worried me the most was how much time it would take, and how much it would interfere with my studies (I was a Ph.D student at the time). It turned out to be quite an undertaking, and it took me a lot longer to finish than I had expected. Luckily, it didn’t interfere too much with my school work, and I managed to get my degree without any delays.

Last year, Jason contacted me again. Apress wanted an expanded and revised version of my book. Was I interested? At the time, I was busy settling into a new position as associate processor, while spending all my spare time portraying Peer Gynt, so again time became the major issue. Eventually (after things had settled down a bit, and I had a bit more time to spare), I agreed to do the book, and this (as I’m sure you’ve gathered) is the result. Most of the material is taken from the first version of the book, Practical Python (Apress, 2002). The existing material has been completely revised, based on recent changes in the Python language, and several new chapters have been added. Some of the old material has also been redistributed to accommodate the new structure. I’ve received a lot of positive feedback from readers about the first version. I hope I’ve been able to keep what people liked and to add more of the same.

Without the persistent help and encouragement from several people, this book would never have been written. My heartfelt thanks go out to all of them. In particular, I would like to thank the team that has worked directly with me in the process of writing the book: Jason Gilmore, for getting the project off the ground and steering it in the right direction; Beckie Stones, for keeping everything together; Jeremy Jones and Matt Moodie for their technical comments and insights; and Linda Marousek for being so patient with me. I’m also grateful to the rest of the team for making the process as smooth as it has been. But this book wouldn’t be what it is without several people who worked with me on the previous version: I’d like to thank Jason Gilmore and Alex Martelli for their excellent technical editing (Jason on the entire book, and Alex on the first half) and for going above and beyond the call of duty in dispensing advice and suggestions; Erin Mulligan and Tory McLearn for holding my hand through the process and for nudging me along when that was needed; Nancy Rapoport for her help polishing my prose; and Grace Wong for providing answers when no one else could. Pete Shinners gave me several helpful suggestions on the game in Project 10, for which I am very grateful. My morale has also been heavily boosted by several encouraging emails from satisfied readers—thanks! Finally, I would like to thank my family and friends, and my girlfriend Ranveig, for putting up with me while I was writing this book.