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Python 3.15.0 candidate 2 is here!

Blog · Watch/Read · (gathered 2026-09-03)

  • Simon Willison highlights the release of Python 3.15.0 candidate 2, urging third-party project maintainers to test their code against it and publish compatible wheels before the final October release.
  • Hugo van Kemenade, the release manager, announced RC2, noting that only clear bug fixes are allowed from now until the final release, and that binary wheels built against RCs will be compatible with future 3.15 versions.
  • Simon emphasizes the critical need for early testing, citing his own experience of finding a bug in Python 3.10 after it shipped because he hadn’t tested during its release candidate phase.
  • Maintainers can easily test against prerelease Python versions in GitHub Actions by using allow-prereleases: true and check-latest: true with actions/setup-python@v7, as demonstrated by Simon’s successful tests for Datasette and sqlite-utils.
  • The primary call to action is for maintainers to prepare their projects and publish Python 3.15 wheels on PyPI now to prevent shipping bugs and to support the broader ecosystem.