From edc723fde186565ace8d404502bc51ca7f8c9796 Mon Sep 17 00:00:00 2001 From: Jelle Zijlstra Date: Wed, 27 Sep 2023 10:35:46 -0700 Subject: [PATCH] Enhance TypedDict docs around required/optional keys (GH-109547) As discussed in comments to GH-109544, the semantics of this attribute are somewhat confusing. Add a note explaining its limitations and steering users towards __required_keys__ and __optional_keys__ instead. (cherry picked from commit f49958c886a2f2608f1008186d588efc2a98b445) Co-authored-by: Jelle Zijlstra --- Doc/library/typing.rst | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index 79f3abd865f6eb..57384b05fe23c9 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -2131,6 +2131,13 @@ types. >>> Point3D.__total__ True + This attribute reflects *only* the value of the ``total`` argument + to the current ``TypedDict`` class, not whether the class is semantically + total. For example, a ``TypedDict`` with ``__total__`` set to True may + have keys marked with :data:`NotRequired`, or it may inherit from another + ``TypedDict`` with ``total=False``. Therefore, it is generally better to use + :attr:`__required_keys__` and :attr:`__optional_keys__` for introspection. + .. attribute:: __required_keys__ .. versionadded:: 3.9 @@ -2166,6 +2173,14 @@ types. .. versionadded:: 3.9 + .. note:: + + If ``from __future__ import annotations`` is used or if annotations + are given as strings, annotations are not evaluated when the + ``TypedDict`` is defined. Therefore, the runtime introspection that + ``__required_keys__`` and ``__optional_keys__`` rely on may not work + properly, and the values of the attributes may be incorrect. + See :pep:`589` for more examples and detailed rules of using ``TypedDict``. .. versionadded:: 3.8