diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index 935a2613626582..0c23a233c0d7dd 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -1469,9 +1469,6 @@ These are not used in annotations. They are building blocks for declaring types. assert Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first') - The type info for introspection can be accessed via ``Point2D.__annotations__``, - ``Point2D.__total__``, ``Point2D.__required_keys__``, and - ``Point2D.__optional_keys__``. To allow using this feature with older versions of Python that do not support :pep:`526`, ``TypedDict`` supports two additional equivalent syntactic forms: @@ -1488,6 +1485,18 @@ These are not used in annotations. They are building blocks for declaring types. The keyword-argument syntax is deprecated in 3.11 and will be removed in 3.13. It may also be unsupported by static type checkers. + The functional syntax should also be used when any of the keys are not valid + :ref:`identifiers`, for example because they are keywords or contain hyphens. + Example:: + + # raises SyntaxError + class Point2D(TypedDict): + in: int # 'in' is a keyword + x-y: int # name with hyphens + + # OK, functional syntax + Point2D = TypedDict('Point2D', {'in': int, 'x-y': int}) + By default, all keys must be present in a ``TypedDict``. It is possible to override this by specifying totality. Usage:: @@ -1504,6 +1513,82 @@ These are not used in annotations. They are building blocks for declaring types. ``True`` as the value of the ``total`` argument. ``True`` is the default, and makes all items defined in the class body required. + It is possible for a ``TypedDict`` type to inherit from one or more other ``TypedDict`` types + using the class-based syntax. + Usage:: + + class Point3D(Point2D): + z: int + + ``Point3D`` has three items: ``x``, ``y`` and ``z``. It is equivalent to this + definition:: + + class Point3D(TypedDict): + x: int + y: int + z: int + + A ``TypedDict`` cannot inherit from a non-TypedDict class, + notably including :class:`Generic`. For example:: + + class X(TypedDict): + x: int + + class Y(TypedDict): + y: int + + class Z(object): pass # A non-TypedDict class + + class XY(X, Y): pass # OK + + class XZ(X, Z): pass # raises TypeError + + T = TypeVar('T') + class XT(X, Generic[T]): pass # raises TypeError + + A ``TypedDict`` can be introspected via annotations dicts + (see :ref:`annotations-howto` for more information on annotations best practices), + :attr:`__total__`, :attr:`__required_keys__`, and :attr:`__optional_keys__`. + + .. attribute:: __total__ + + ``Point2D.__total__`` gives the value of the ``total`` argument. + Example:: + + >>> from typing import TypedDict + >>> class Point2D(TypedDict): pass + >>> Point2D.__total__ + True + >>> class Point2D(TypedDict, total=False): pass + >>> Point2D.__total__ + False + >>> class Point3D(Point2D): pass + >>> Point3D.__total__ + True + + .. attribute:: __required_keys__ + .. attribute:: __optional_keys__ + + ``Point2D.__required_keys__`` and ``Point2D.__optional_keys__`` return + :class:`frozenset` objects containing required and non-required keys, respectively. + Currently the only way to declare both required and non-required keys in the + same ``TypedDict`` is mixed inheritance, declaring a ``TypedDict`` with one value + for the ``total`` argument and then inheriting it from another ``TypedDict`` with + a different value for ``total``. + Usage:: + + >>> class Point2D(TypedDict, total=False): + ... x: int + ... y: int + ... + >>> class Point3D(Point2D): + ... z: int + ... + >>> Point3D.__required_keys__ == frozenset({'z'}) + True + >>> Point3D.__optional_keys__ == frozenset({'x', 'y'}) + True + See :pep:`589` for more examples and detailed rules of using ``TypedDict``. .. versionadded:: 3.8