We're sunsetting PodQuest on 2025-07-28. Thank you for your support!
Export Podcast Subscriptions
cover of episode #436 Slow tests go last

#436 Slow tests go last

2025/6/16
logo of podcast Python Bytes

Python Bytes

AI Deep Dive AI Chapters Transcript
People
B
Brian
Python 开发者和播客主持人,专注于测试和软件开发教育。
M
Michael
帮助医生和高收入专业人士管理财务的金融教育者和播客主持人。
Topics
Brian: 我认为Python 3.14中自由线程不再是实验性的是一个令人鼓舞的消息,这意味着我们已经准备好支持它。虽然第二阶段还有很多工作要做,例如确保API ABI的兼容性、性能和内存护栏,但社区对自由线程的广泛采用充满信心。不过,成为默认设置至少还需要几年时间,因为稳定ABI支持的要求。我个人对自由线程的未来发展感到兴奋。 Michael: 我也非常期待自由线程的到来,它开启了很多有趣的机会。目前,如果不进行显式的多进程处理,Python代码只能利用10%的计算资源,而自由线程能够并行运行代码而无需序列化到多个进程,这非常棒。然而,人们在编写Python或其他语言代码时,往往没有充分考虑线程安全问题。我认为复杂性在于库,而不是应用程序,作为库的开发者,你不能决定你的库是否被用于多线程环境。我们不希望失去Python的易用性。

Deep Dive

Chapters
The Python community celebrates the removal of the "experimental" tag from free-threaded Python in 3.14. However, it's a multi-year journey to become the default, requiring API/ABI stability, documentation enhancements, and community adoption. The discussion covers thread safety considerations and potential challenges for library developers.
  • Free-threaded Python is no longer experimental in Python 3.14.
  • Becoming the default build will take several years.
  • Thread safety and documentation are crucial for broader adoption.

Shownotes Transcript

Topics covered in this episode:

- ** Free-threaded Python no longer “experimental” as of Python 3.14**

Watch on YouTube)

About the show

Sponsored by PropelAuth: pythonbytes.fm/propelauth66)

Connect with the hosts

Join us on YouTube at pythonbytes.fm/live) to be part of the audience. Usually Monday at 10am PT. Older video versions available there too.

Finally, if you want an artisanal, hand-crafted digest of every week of the show notes in email form? Add your name and email to our friends of the show list), we'll never share it.

Brian #1: Free-threaded Python no longer “experimental” as of Python 3.14

  • “PEP 779 ("Criteria for supported status for free-threaded Python") has been accepted, which means free-threaded Python is now a supported build!” - Hugo van Kemenade)

  • PEP 779 – Criteria for supported status for free-threaded Python)

  • As noted in the discussion of PEP 779), “The Steering Council (SC) approves PEP 779, with the effect of removing the “experimental” tag from the free-threaded build of Python 3.14.”

  • We are in Phase II then.

  • “We are confident that the project is on the right path, and we appreciate the continued dedication from everyone working to make free-threading ready for broader adoption across the Python community.”

  • “Keep in mind that any decision to transition to Phase III, with free-threading as the default or sole build of Python is still undecided, and dependent on many factors both within CPython itself and the community. We leave that decision for the future.”

  • How long will all this take? According to Thomas Wouters, a few years, at least): “In other words: it'll be a few years at least. It can't happen before 3.16 (because we won't have Stable ABI support until 15) and may well take longer.”

Michael #2: typed-ffmpeg)

- typed-ffmpeg offers a modern, Pythonic interface to FFmpeg, providing extensive support for complex filters with detailed typing and documentation.

- Inspired by ffmpeg-python, this package enhances functionality by addressing common limitations, such as lack of IDE integration and comprehensive typing, while also introducing new features like JSON serialization of filter graphs and automatic FFmpeg validation.

- Features :

  • Zero Dependencies: Built purely with the Python standard library, ensuring maximum compatibility and security.

  • User-Friendly: Simplifies the construction of filter graphs with an intuitive Pythonic interface.

  • Comprehensive FFmpeg Filter Support: Out-of-the-box support for most FFmpeg filters, with IDE auto-completion.

  • Integrated Documentation: In-line docstrings provide immediate reference for filter usage, reducing the need to consult external documentation.

  • Robust Typing: Offers static and dynamic type checking, enhancing code reliability and development experience.

  • Filter Graph Serialization: Enables saving and reloading of filter graphs in JSON format for ease of use and repeatability.

  • Graph Visualization: Leverages graphviz for visual representation, aiding in understanding and debugging.

  • Validation and Auto-correction: Assists in identifying and fixing errors within filter graphs.

  • Input and Output Options Support: Provide a more comprehensive interface for input and output options, including support for additional codecs and formats.

  • Partial Evaluation: Enhance the flexibility of filter graphs by enabling partial evaluation, allowing for modular construction and reuse.

  • Media File Analysis: Built-in support for analyzing media files using FFmpeg's ffprobe utility, providing detailed metadata extraction with both dictionary and dataclass interfaces.

Michael #3: pyleak)

  • Detect leaked asyncio tasks, threads, and event loop blocking with stack trace in Python. Inspired by goleak.

  • Use as context managers or function dectorators

  • When using no_task_leaks, you get detailed stack trace information showing exactly where leaked tasks are executing and where they were created.

  • Even has great examples and a pytest plugin.

Brian #4: Optimizing Test Execution: Running live_server Tests Last with pytest)

- Tim Kamanin

- “When working with Django applications, it's common to have a mix of fast unit tests and slower end-to-end (E2E) tests that use pytest's live_server fixture and browser automation tools like Playwright or Selenium. ”

- Tim is running E2E tests last for

  • Faster feedback from quick tests

  • To not tie up resources early in the test suite.

He did this with

- custom “e2e” marker

- Implementing a

`pytest_collection_modifyitems
`

hook function to look for tests using the

`live_server
`

fixture, and for them

  • automatically add the e2e marker to those tests

  • move those tests to the end

The reason for the marker is to be able to

  • Just run e2e tests with -m e2e

  • Avoid running them sometimes with -m "not e2e"

Cool small writeup.

  • The technique works for any system that has some tests that are slower or resource bound based on a particular fixture or set of fixtures.

Extras

Brian:

Michael:

Joke: Naming is hard)