# Documentation (A clear and concise description of the issue.) The function signature mismatch for `functools.reduce`: - C implementation: ```python _initial_missing = object() @overload def reduce(function, iterable, /): ... @overload def reduce(function, iterable, initial=_initial_missing, /): ... ``` - Python implementation: ```python _initial_missing = object() @overload def reduce(function, sequence): ... @overload def reduce(function, sequence, initial=_initial_missing): ... ``` Argument change: `iterable -> sequence`. - Online documentation: ```python def reduce(function, iterable, initializer=None): ... ``` Argument change: `initial -> initializer`. <!-- gh-linked-prs --> ### Linked PRs * gh-102759 <!-- /gh-linked-prs -->