An assignment expression—also known as the walrus operator—is a new syntax introduced in Python 3.8 to solve a long-standing problem with the language that can cause code duplication. Whereas normal assignment statements are written a = b and pronounced “a equals b”, these assignments are written a := b and pronounced “a walrus b” (because := looks like a pair of eyeballs and tusks). Continue reading »

Although metaclasses allow you to customize class creation in multiple ways (see Item 48: “Validate Subclasses with __init_subclass__” and Item 49: “Register Class Existence with __init_subclass__”), they still fall short of handling every situation that may arise. Continue reading »

You can immediately read the second edition of Effective Python as a DRM-free eBook, on Kindle, on Google Play, and on O’Reilly Online Learning.

Though Python isn’t able to parallelize CPU-bound computation without extra effort (see Item 64: “Consider concurrent.futures for True Parallelism”), it is able to support high-throughput, parallel I/O in a variety of ways (see Item 53: “Use Threads for Blocking I/O, Avoid for Parallelism” and Item 60: “Achieve Highly Concurrent I/O with Coroutines” for details). That said, it’s surprisingly easy to use these I/O tools the wrong way and reach the conclusion that the language is too slow for even I/O-bound workloads. Continue reading »

Effective Python: Second Edition is now available for preorder. Follow this link to buy your copy in advance. It will ship in mid-November (2019) once the book has finished printing and is stocked in the warehouse. Digital editions will become available when the physical book ships or sooner.