python / python/cpython

`fnmatch.translate` changed in an undocumented way in Python 3.14

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Since Mar 15, 2026.

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Description

Documentation

Since Python 3.14, fnmatch.translate appends a lowercase z, whilst 3.13 and below used an uppercase Z.
https://docs.python.org/3/library/fnmatch.html#fnmatch.translate makes no mention of this. Searching for fnmatch in https://docs.python.org/3/whatsnew/3.14.html only finds https://docs.python.org/3/whatsnew/3.14.html#fnmatch .

> uvx --python=3.13 python -c "import fnmatch; print(fnmatch.translate('foo*'))"
(?s:foo.*)\Z
> uvx --python=3.14 python -c "import fnmatch; print(fnmatch.translate('foo*'))"
(?s:foo.*)\z

(noticed in https://github.com/pypa/distutils/issues/381)


Edit:
After further research, the only mention I could find in "What's new in Python 3.14" is https://docs.python.org/3/whatsnew/3.14.html#re, which only says

Support \z as a synonym for \Z

not that \z is now also used in place of \Z.
https://docs.python.org/3/howto/regex.html#more-metacharacters does mention that

\Z
The same as \z. For compatibility with old Python versions.

Up to you to see if this is worth acting upon. It did confuse me and I had a bit of a hard time finding reference for this change. But I understand if it's considered "implementation detail" and that distutils (setuptools)'s test validating a regex is too niche of a use-case to be worth documenting.

Linked PRs
  • gh-144457

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