https://github.com/python/cpython/commit/a178445a46e675830a10518a4d90232d710e1666 commit: a178445a46e675830a10518a4d90232d710e1666 branch: 3.12 author: Miss Islington (bot) <[email protected]> committer: AlexWaygood <[email protected]> date: 2024-09-27T14:17:37-07:00 summary:
[3.12] gh-90190: Add doc for using `singledispatch` with precise collection type hints (GH-116544) (#124711) Co-authored-by: Matt Delengowski <[email protected]> files: M Doc/library/functools.rst diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst index a118dee92fed3c..4bd2ecd9332b23 100644 --- a/Doc/library/functools.rst +++ b/Doc/library/functools.rst @@ -490,6 +490,25 @@ The :mod:`functools` module defines the following functions: ... print(arg.real, arg.imag) ... + For code that dispatches on a collections type (e.g., ``list``), but wants + to typehint the items of the collection (e.g., ``list[int]``), the + dispatch type should be passed explicitly to the decorator itself with the + typehint going into the function definition:: + + >>> @fun.register(list) + ... def _(arg: list[int], verbose=False): + ... if verbose: + ... print("Enumerate this:") + ... for i, elem in enumerate(arg): + ... print(i, elem) + + .. note:: + + At runtime the function will dispatch on an instance of a list regardless + of the type contained within the list i.e. ``[1,2,3]`` will be + dispatched the same as ``["foo", "bar", "baz"]``. The annotation + provided in this example is for static type checkers only and has no + runtime impact. To enable registering :term:`lambdas<lambda>` and pre-existing functions, the :func:`register` attribute can also be used in a functional form:: _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-checkins.python.org/ Member address: [email protected]
