Python 3.15.0 candidate 2 is here!
- ID
- 20270
- Status
- summarized
- Published
- 01 Sep 2026, 10:59 PM
- Fetched
- 02 Sep 2026, 2:44 PM
- Provider
- Simon Willison
- Category
- developer-ai
- Original URL
- https://simonwillison.net/2026/Sep/1/python-315-rc-2/
- Source URL
- https://simonwillison.net/atom/everything/
Summary
- Score
- 6.5
- Created
- 02 Sep 2026, 2:44 PM
- Tags
- Audience
- developersvibe_coders
What happened
Python 3.15.0 release candidate 2 is announced by release manager Hugo van Kemenade, with final release scheduled for October 2026. Only bug fixes are allowed between now and the final release, and maintainers are urged to build and publish 3.15 wheels on PyPI now. Simon Willison notes the RC isn't on GitHub Actions yet but provides a concrete CI matrix snippet using allow-prereleases and check-latest flags to auto-track RC versions.
Why it matters
If you ship a Python package or maintain a Python-based service, add 3.15 RC to your CI matrix now using the provided actions/setup-python config with allow-prereleases: true so you catch breakages before the October stable release. Binary wheels built against RC2 will remain compatible with the final 3.15.0.
Discussion angle
Walk through the exact GitHub Actions matrix snippet and discuss whether your team's current CI pipeline is set up to catch pre-release Python breakages, or if you're only testing against stable versions and discovering issues too late.