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20 changes: 16 additions & 4 deletions Doc/howto/annotations.rst
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Expand Up @@ -243,10 +243,22 @@ If you use a class with a custom metaclass and access ``__annotations__``
on the class, you may observe unexpected behavior; see
:pep:`749 <749#pep749-metaclasses>` for some examples. You can avoid these
quirks by using :func:`annotationlib.get_annotations` on Python 3.14+ or
:func:`inspect.get_annotations` on Python 3.10+. On earlier versions of
Python, you can avoid these bugs by accessing the annotations from the
class's :attr:`~type.__dict__`
(for example, ``cls.__dict__.get('__annotations__', None)``).
:func:`inspect.get_annotations` on Python 3.10+.

.. note::

On Python 3.14 and later, annotations are evaluated lazily (see
:pep:`649` and :pep:`749`), and how the annotations dict is stored in
the class's :attr:`~type.__dict__` is a private implementation detail.
Reading ``cls.__dict__.get('__annotations__', None)`` may therefore
return ``None`` even when the class has annotations. On these versions,
always use :func:`annotationlib.get_annotations` (or
:func:`inspect.get_annotations`) rather than accessing
:attr:`~type.__dict__` directly.

Only on Python 3.9 and earlier, where neither function is available, can you
avoid these bugs by reading the annotations from the class's
:attr:`~type.__dict__` (for example, ``cls.__dict__.get('__annotations__', None)``).

In some versions of Python, instances of classes may have an ``__annotations__``
attribute. However, this is not supported functionality. If you need the
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