Book Image

Mastering Python 2E - Second Edition

By : Rick van Hattem
5 (1)
Book Image

Mastering Python 2E - Second Edition

5 (1)
By: Rick van Hattem

Overview of this book

Even if you find writing Python code easy, writing code that is efficient, maintainable, and reusable is not so straightforward. Many of Python’s capabilities are underutilized even by more experienced programmers. Mastering Python, Second Edition, is an authoritative guide to understanding advanced Python programming so you can write the highest quality code. This new edition has been extensively revised and updated with exercises, four new chapters and updates up to Python 3.10. Revisit important basics, including Pythonic style and syntax and functional programming. Avoid common mistakes made by programmers of all experience levels. Make smart decisions about the best testing and debugging tools to use, optimize your code’s performance across multiple machines and Python versions, and deploy often-forgotten Python features to your advantage. Get fully up to speed with asyncio and stretch the language even further by accessing C functions with simple Python calls. Finally, turn your new-and-improved code into packages and share them with the wider Python community. If you are a Python programmer wanting to improve your code quality and readability, this Python book will make you confident in writing high-quality scripts and taking on bigger challenges
Table of Contents (21 chapters)
19
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20
Index

Debugging asyncio

The asyncio module has a few special provisions to make debugging somewhat easier. Given the asynchronous nature of functions within asyncio, this is a very welcome feat. While the debugging of multithreaded/multiprocessing functions or classes can be difficult – since concurrent classes can easily change environment variables in parallel – with asyncio, it’s just as difficult, if not more, because asyncio background tasks run in the stack of the event loop, not your own stack.

If you wish to skip this part of the chapter, I urge you to at least read the section on Exiting before all tasks are done. That covers a huge pitfall with asyncio.

The first and most obvious way of debugging asyncio is to use the event loop debug mode. We have several options for enabling the debug mode:

  • Set the PYTHONASYNCIODEBUG environment variable to True
  • Enable the Python development mode using the PYTHONDEVMODE environment...