https://github.com/python/cpython/commit/7291eaba8b20b19e7971d43d88286d5820e5eb56
commit: 7291eaba8b20b19e7971d43d88286d5820e5eb56
branch: main
author: Jelle Zijlstra <jelle.zijls...@gmail.com>
committer: JelleZijlstra <jelle.zijls...@gmail.com>
date: 2025-05-26T08:35:04-07:00
summary:
gh-119180: Updates to PEP 649/749 docs (#134640)
- Mention (again) that `type.__annotations__` is unsafe. It is now safe
when using only classes defined under PEP 649 semantics, but not with
classes defined using `from __future__ import annotations`.
- Mention that annotations on instances no longer work. There was already
an issue about this.
- Mention the general changes in the "Porting to Python 3.14" section.
- `annotationlib` was proposed by PEP-749, not PEP-649.
Co-authored-by: Emma Smith <e...@emmatyping.dev>
Co-authored-by: Carol Willing <carolc...@willingconsulting.com>
files:
M Doc/reference/datamodel.rst
M Doc/whatsnew/3.14.rst
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 005a768f684e2c..32a2e266262c52 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1228,10 +1228,22 @@ Special attributes
:attr:`__annotations__ attributes <object.__annotations__>`.
For best practices on working with :attr:`~object.__annotations__`,
- please see :mod:`annotationlib`. Where possible, use
+ please see :mod:`annotationlib`. Use
:func:`annotationlib.get_annotations` instead of accessing this
attribute directly.
+ .. warning::
+
+ Accessing the :attr:`!__annotations__` attribute directly
+ on a class object may return annotations for the wrong class,
specifically
+ in certain cases where the class, its base class, or a metaclass
+ is defined under ``from __future__ import annotations``.
+ See :pep:`749 <749#pep749-metaclasses>` for details.
+
+ This attribute does not exist on certain builtin classes. On
+ user-defined classes without ``__annotations__``, it is an
+ empty dictionary.
+
.. versionchanged:: 3.14
Annotations are now :ref:`lazily evaluated <lazy-evaluation>`.
See :pep:`649`.
diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
index 88e52015bdc2b1..561d1a8914b50c 100644
--- a/Doc/whatsnew/3.14.rst
+++ b/Doc/whatsnew/3.14.rst
@@ -74,7 +74,7 @@ deferred evaluation of annotations (:pep:`649`),
and a new type of interpreter that uses tail calls.
The library changes include the addition of a new :mod:`!annotationlib` module
-for introspecting and wrapping annotations (:pep:`649`),
+for introspecting and wrapping annotations (:pep:`749`),
a new :mod:`!compression.zstd` module for Zstandard support (:pep:`784`),
plus syntax highlighting in the REPL,
as well as the usual deprecations and removals,
@@ -444,6 +444,10 @@ In particular, do not read annotations directly from the
namespace dictionary
attribute of type objects. Use
:func:`annotationlib.get_annotate_from_class_namespace`
during class construction and :func:`annotationlib.get_annotations` afterwards.
+In previous releases, it was sometimes possible to access class annotations
from
+an instance of an annotated class. This behavior was undocumented and
accidental,
+and will no longer work in Python 3.14.
+
``from __future__ import annotations``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -2501,6 +2505,11 @@ Changes in the Python API
See :ref:`above <whatsnew314-typing-union>` for more details.
(Contributed by Jelle Zijlstra in :gh:`105499`.)
+* The runtime behavior of annotations has changed in various ways; see
+ :ref:`above <whatsnew314-pep649>` for details. While most code that interacts
+ with annotations should continue to work, some undocumented details may
behave
+ differently.
+
Build changes
=============
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