Jacob Zimmerman - Python Descriptors: Understanding and Using the Descriptor Protocol

Superscript letters like the one at the end of the previous line are in reference to the bibliography at the back of the book, which includes URLs to the referenced site.

When the text mentions class and instance in a general sense, they refer to a class that has a descriptor attribute and to instances of such classes, respectively. All other classes and instances will be referred to more specifically.

The 2 nd edition is an update including new features of Python as well as new ideas to learn. One of the new things is incredibly important if this book wants to maintain the status of comprehensive guide that it strives for. This important addition is about the addition of __set_name__() to the descriptor protocol in Python 3.6. You can read about this in Chapter , Storing the Attributes.

Another addition is an idea that was inspired by looking into the __set_name__() addition to the protocol, which youll see just after the section on that addition. Also, I added a chapter on creating instance-level descriptors, which were added to descriptor-tools well before this edition really got started.

The next thing is actually a change, not an addition. Since writing the first book, I found out about the built-in function vars() . Calling vars(obj) is equivalent to obj.__dict__ , but is more Pythonic. Kind of like calling len(obj) instead of obj.__len__() . So the code examples have been updated to use vars() . Any remaining references to __dict__ are purposeful.

Pretty much everything else new in this edition is just cleaning up the language to be more legible.

In order to be sure that I got everything rightit would really suck for a comprehensive guide to be missing a big chunk of functionality or to get anything wrongI enlisted the help of some Python experts on the first edition. In return for their help, I let them introduce themselves to you here. Thats not all I did in return, but its all youre going to see:)

Emanuel Barry is a self-taught Python programmer who loves pushing the language to its limits as well as exploring its darkest corners. He has to do a lot of proofreading and editing for a local non-for-profit organization, and decided to combine his love of Python and knowledge sharing with his background in proofreading to help make this book even better. He can often be found in the shadows of the mailing lists or the issue tracker, as well as the Python IRC channel, as Vgr.

Chris Angelico has played around with Python since the late 90s, getting more serious with the language in the mid 2000s. As a PEP Editor and active participant in the various mailing lists, he keeps well up to date with whats new and upcoming in the language and also shares that knowledge with fledgling students in the Thinkful tutoring/mentoring program. When not coding in Python, he is often found wordsmithing for a Dungeons & Dragons campaign, or exploring the linguistic delights of Alice in Wonderland and similar works. If you find a subtle Alice reference in this text, blame him!

https://github.com/Rosuav

Kevin Mackay is a software engineer who has been programming in Python since 2010 and is currently working at BBC, improving the Taster platform. He is enthusiastic about open source software and occasionally contributes to the 3D graphics application, Blender. He can be found on the Python IRC channel as yakca or hiking on a mountain somewhere in Scotland.