gh-97797: Mention __metadata__ in docstrings of `typing.{_Annotated…

…Alias, Annotated}`
python · AlexWaygood · Apr 10, 2023 · Apr 10, 2023 · Apr 10, 2023 · Apr 10, 2023
commit 90106965fa574b229bdc034236a9626fb8b2a2f4
@@ -2154,6 +2154,8 @@ class _AnnotatedAlias(_NotIterable, _GenericAlias, _root=True):
    with extra annotations. The alias behaves like a normal typing alias,
    instantiating is the same as instantiating the underlying type, binding
    it to types is also the same.
+
+    The metadata itself is storred in '__metadata__' attribute as a tuple.
    """
    def __init__(self, origin, metadata):
        if isinstance(origin, _AnnotatedAlias):
@@ -2209,6 +2211,10 @@ class Annotated:
    Details:

    - It's an error to call `Annotated` with less than two arguments.
+    - Metadata can be accessed in runtime with::
+
+        Annotated[int, '$'].__metadata__ == ('$',)
+
    - Nested Annotated are flattened::

        Annotated[Annotated[T, Ann1, Ann2], Ann3] == Annotated[T, Ann1, Ann2, Ann3]