Richard Jones' Log: Review: Lennart Regebro's "Porting to Python 3"

Lennart Regebro has provided me with a free copy of his self-published book "Porting to Python 3" so that I may review it. He has considerable experience in porting code from Python 2 to Python 3, and it shows in much of his advice and examples. Regebro has assembled an excellent cast of helpers: the technical reviewer Martin von L�wis also has much expertise with Python 3 (he implemented the first port of the popular Django web framework). Brett Canon's introduction also provides a good starting point for someone new to the story of Python 3.

The book's structure is well thought-out. The first chapter immediately invites the reader to make sure they really need to port their code, and what considerations might be taken into account when deciding to do so. The book even has advice, backed up with useful information, for those who are currently unable to port their code but may start preparing for doing so in the future.

The second chapter discusses strategies for moving to Python 3 (view it online). These are presented clearly with one section per strategy. Within each section there are clear references to the other, more detailed chapters of the book which may be used to implement each strategy.

Once you've decided which strategy to apply you can focus on the pertinent remaining chapters. These follow a pretty logical progression:

• firstly preparing the way by making your code more modern,
• introducing the 2to3 tool for automatically converting code to Python 3 and the various options for how to use it,
• talking through some common migration problems and some simple solutions to them,
• presenting some modern Python (2.6+) idioms that your code may use in Python 2 and 3, and
• supporting Python 2 and 3 without using the 2to3 tool.

The final two chapters are for more limited audiences and cover migrating C extensions and writing custom 2to3 tool fixers. Even though these are topics which most readers won't need to worry about they are still covered in good detail with minimum fuss. It is in this final chapter that Regebro's experience with porting gives weight to the advice and examples he presents.

Finally there's a couple of pretty comprehensive appendices covering over the main language incompatibilities and library changes which makes it a good reference.

As previously mentioned, the book is very well-organised giving the reader an easy path through the material depending on their situation. Throughout the book there are many pertinent and clear references to software written by others. The book suffers from some typesetting and grammatical errors, though these are minor and none could cause any confusion regarding the content.

CONCLUSION
There's a lot of information out there for porting from Python 2 to 3, but Regebro has produced a concise, well-organised and complete reference for doing so. It's not skimped on any detail though; the book covers all areas related to moving to Python 3. It's not just about porting code; it's also a handy book for any programmer who's grown up with Python 2 (or 1!) and is looking to move to Python 3.