gh-121676: Raise a ``DeprecationWarning`` if the Python implementation of ``functools.reduce`` is called with `function` or `sequence` as a keyword args (#121677)

Python implementation of `functools` allows calling `reduce`
with `function` or `sequence` as keyword args. This doesn't
match behavior of our C accelerator and our documentation
for `functools.reduce` states that `function`and `sequence`
are positional-only arguments.

Now calling a Python implementation of `functools.reduce`
with `function` or `sequence` as keyword args would raise
a `DeprecationWarning` and is planned to be prohibited in
Python 3.16.


Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Library/2024-07-13-13-25-31.gh-issue-121676.KDLS11.rst b/Misc/NEWS.d/next/Library/2024-07-13-13-25-31.gh-issue-121676.KDLS11.rst
new file mode 100644
index 0000000..be589b7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-07-13-13-25-31.gh-issue-121676.KDLS11.rst
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+Deprecate calling the Python implementation of :meth:`functools.reduce`
+with a ``function`` or ``sequence`` as a :term:`keyword argument`.
+This will be forbidden in Python 3.16 in order to match the C implementation.