diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index 0dc71d479592eb..c63375d048ae45 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -719,8 +719,8 @@ The :data:`Any` type ==================== A special kind of type is :data:`Any`. A static type checker will treat -every type as being compatible with :data:`Any` and :data:`Any` as being -compatible with every type. +every type as assignable to :data:`Any` and :data:`Any` as assignable to +every type. This means that it is possible to perform any operation or method call on a value of type :data:`Any` and assign it to any variable:: @@ -785,7 +785,7 @@ it as a return value) of a more specialized type is a type error. For example:: hash_a(42) hash_a("foo") - # Passes type checking, since Any is compatible with all types + # Passes type checking, since Any is assignable to all types hash_b(42) hash_b("foo") @@ -851,8 +851,8 @@ using ``[]``. Special type indicating an unconstrained type. - * Every type is compatible with :data:`Any`. - * :data:`Any` is compatible with every type. + * Every type is assignable to :data:`Any`. + * :data:`Any` is assignable to every type. .. versionchanged:: 3.11 :data:`Any` can now be used as a base class. This can be useful for @@ -1284,10 +1284,10 @@ These can be used as types in annotations. They all support subscription using :data:`ClassVar` accepts only types and cannot be further subscribed. - :data:`ClassVar` is not a class itself, and should not + :data:`ClassVar` is not a class itself, and cannot be used with :func:`isinstance` or :func:`issubclass`. :data:`ClassVar` does not change Python runtime behavior, but - it can be used by third-party type checkers. For example, a type checker + it can be used by static type checkers. For example, a type checker might flag the following code as an error:: enterprise_d = Starship(3000) @@ -1357,7 +1357,7 @@ These can be used as types in annotations. They all support subscription using def mutate_movie(m: Movie) -> None: m["year"] = 1999 # allowed - m["title"] = "The Matrix" # typechecker error + m["title"] = "The Matrix" # type checker error There is no runtime checking for this property. @@ -2283,9 +2283,9 @@ types. Fields with a default value must come after any fields without a default. - The resulting class has an extra attribute ``__annotations__`` giving a - dict that maps the field names to the field types. (The field names are in - the ``_fields`` attribute and the default values are in the + The types for each field name can be retrieved by calling + :func:`inspect.get_annotations` on the resulting class. (The field names + are in the ``_fields`` attribute and the default values are in the ``_field_defaults`` attribute, both of which are part of the :func:`~collections.namedtuple` API.) @@ -2355,7 +2355,7 @@ types. Helper class to create low-overhead :ref:`distinct types `. - A ``NewType`` is considered a distinct type by a typechecker. At runtime, + A ``NewType`` is considered a distinct type by a type checker. At runtime, however, calling a ``NewType`` returns its argument unchanged. Usage:: @@ -2430,7 +2430,7 @@ types. Mark a protocol class as a runtime protocol. Such a protocol can be used with :func:`isinstance` and :func:`issubclass`. - This allows a simple-minded structural check, very similar to "one trick ponies" + This allows a simple-minded structural check, very similar to "one-trick ponies" in :mod:`collections.abc` such as :class:`~collections.abc.Iterable`. For example:: @runtime_checkable @@ -2621,7 +2621,7 @@ types. key: T group: list[T] - A ``TypedDict`` can be introspected via annotations dicts + A ``TypedDict`` can be introspected via :func:`inspect.get_annotations` (see :ref:`annotations-howto` for more information on annotations best practices), :attr:`__total__`, :attr:`__required_keys__`, and :attr:`__optional_keys__`. @@ -2664,7 +2664,7 @@ types. For backwards compatibility with Python 3.10 and below, it is also possible to use inheritance to declare both required and - non-required keys in the same ``TypedDict`` . This is done by declaring a + non-required keys in the same ``TypedDict``. This is done by declaring a ``TypedDict`` with one value for the ``total`` argument and then inheriting from it in another ``TypedDict`` with a different value for ``total``: @@ -2746,34 +2746,34 @@ with :deco:`runtime_checkable`. .. class:: SupportsAbs - An ABC with one abstract method ``__abs__`` that is covariant + A protocol with one abstract method ``__abs__`` that is covariant in its return type. .. class:: SupportsBytes - An ABC with one abstract method ``__bytes__``. + A protocol with one abstract method ``__bytes__``. .. class:: SupportsComplex - An ABC with one abstract method ``__complex__``. + A protocol with one abstract method ``__complex__``. .. class:: SupportsFloat - An ABC with one abstract method ``__float__``. + A protocol with one abstract method ``__float__``. .. class:: SupportsIndex - An ABC with one abstract method ``__index__``. + A protocol with one abstract method ``__index__``. .. versionadded:: 3.8 .. class:: SupportsInt - An ABC with one abstract method ``__int__``. + A protocol with one abstract method ``__int__``. .. class:: SupportsRound - An ABC with one abstract method ``__round__`` + A protocol with one abstract method ``__round__`` that is covariant in its return type. ABCs for working with IO @@ -3432,7 +3432,7 @@ Constant .. data:: TYPE_CHECKING - A special constant that is assumed to be ``True`` by 3rd party static + A special constant that is assumed to be ``True`` by static type checkers. It is ``False`` at runtime. Usage:: diff --git a/Lib/typing.py b/Lib/typing.py index 629204cf63adbd..32a7b9f9b07982 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -5,7 +5,7 @@ * Generic, Protocol, and internal machinery to support generic aliases. All subscripted types like X[int], Union[int, str] are generic aliases. * Various "special forms" that have unique meanings in type annotations: - NoReturn, Never, ClassVar, Self, Concatenate, Unpack, and others. + Any, Never, ClassVar, Self, Concatenate, Unpack, and others. * Classes whose instances can be type arguments to generic classes and functions: TypeVar, ParamSpec, TypeVarTuple. * Public helper functions: get_type_hints, overload, cast, final, and others. @@ -598,12 +598,12 @@ def __repr__(self): class Any(metaclass=_AnyMeta): """Special type indicating an unconstrained type. - - Any is compatible with every type. - - Any assumed to have all methods. - - All values assumed to be instances of Any. + - Any is assignable to every type. + - Any assumed to have all methods and attributes. + - All values are assignable to Any. Note that all the above statements are true from the point of view of - static type checkers. At runtime, Any should not be used with instance + static type checkers. At runtime, Any cannot be used with instance checks. """ @@ -722,7 +722,7 @@ class Starship: ClassVar accepts only types and cannot be further subscribed. - Note that ClassVar is not a class itself, and should not + Note that ClassVar is not a class itself, and cannot be used with isinstance() or issubclass(). """ item = _type_check(parameters, f'{self} accepts only single type.', allow_special_forms=True) @@ -805,7 +805,7 @@ def _make_union(left, right): @_SpecialForm def Optional(self, parameters): - """Optional[X] is equivalent to Union[X, None].""" + """Optional[X] is equivalent to X | None.""" arg = _type_check(parameters, f"{self} requires a single type.") return Union[arg, type(None)] @@ -848,7 +848,7 @@ def open_helper(file: str, mode: MODE) -> str: def TypeAlias(self, parameters): """Special form for marking type aliases. - Use TypeAlias to indicate that an assignment should + TypeAlias can be used to indicate that an assignment should be recognized as a proper type alias definition by type checkers. @@ -1881,7 +1881,7 @@ class Movie(TypedDict): def foo(**kwargs: Unpack[Movie]): ... Note that there is only some runtime checking of this operator. Not - everything the runtime allows may be accepted by static type checkers. + everything the runtime allows is accepted by static type checkers. For more information, see PEPs 646 and 692. """ @@ -2347,7 +2347,7 @@ def runtime_checkable(cls): Such protocol can be used with isinstance() and issubclass(). Raise TypeError if applied to a non-protocol class. This allows a simple-minded structural check very similar to - one trick ponies in collections.abc such as Iterable. + one-trick ponies in collections.abc such as Iterable. For example:: @@ -2418,8 +2418,8 @@ def greet(name: str) -> None: def get_type_hints(obj, globalns=None, localns=None, include_extras=False): """Return type hints for an object. - This is often the same as obj.__annotations__, but it handles - forward references encoded as string literals and recursively replaces all + This is often the same as inspect.get_annotations(obj) or obj.__annotations__, + but it handles forward references encoded as string literals and recursively replaces all 'Annotated[T, ...]' with 'T' (unless 'include_extras=True'). The argument may be a module, class, method, or function. The annotations @@ -2601,7 +2601,7 @@ def get_args(tp): def is_typeddict(tp): - """Check if an annotation is a TypedDict class. + """Check if an object is a TypedDict class. For example:: @@ -2715,10 +2715,10 @@ def _overload_dummy(*args, **kwds): def overload(func): """Decorator for overloaded functions/methods. - In a stub file, place two or more stub definitions for the same - function in a row, each decorated with @overload. - - For example:: + In a non-stub file, place two or more stub definitions for the same + function in a row, each decorated with @overload, followed + by an implementation. The implementation should *not* + be decorated with @overload:: @overload def utf8(value: None) -> None: ... @@ -2726,10 +2726,11 @@ def utf8(value: None) -> None: ... def utf8(value: bytes) -> bytes: ... @overload def utf8(value: str) -> bytes: ... + def utf8(value): + ... # implementation goes here - In a non-stub file (i.e. a regular .py file), do the same but - follow it with an implementation. The implementation should *not* - be decorated with @overload:: + In a stub file or in an abstract method (for example, in a Protocol definition), + the implementation may be omitted:: @overload def utf8(value: None) -> None: ... @@ -2737,8 +2738,6 @@ def utf8(value: None) -> None: ... def utf8(value: bytes) -> bytes: ... @overload def utf8(value: str) -> bytes: ... - def utf8(value): - ... # implementation goes here The overloads for a function can be retrieved at runtime using the get_overloads() function. @@ -2774,7 +2773,7 @@ def final(f): """Decorator to indicate final methods and final classes. Use this decorator to indicate to type checkers that the decorated - method cannot be overridden, and decorated class cannot be subclassed. + method cannot be overridden, and the decorated class cannot be subclassed. For example:: @@ -2816,7 +2815,7 @@ class Other(Leaf): # Error reported by type checker V_co = TypeVar('V_co', covariant=True) # Any type covariant containers. VT_co = TypeVar('VT_co', covariant=True) # Value type covariant containers. T_contra = TypeVar('T_contra', contravariant=True) # Ditto contravariant. -# Internal type variable used for Type[]. +# Internal type bound to class object types. CT_co = TypeVar('CT_co', covariant=True, bound=type) @@ -2907,7 +2906,7 @@ class TeamUser(User): ... And a function that takes a class argument that's a subclass of User and returns an instance of the corresponding class:: - def new_user[U](user_class: Type[U]) -> U: + def new_user[U](user_class: type[U]) -> U: user = user_class() # (Here we could write the user object to a database) return user @@ -2920,7 +2919,7 @@ def new_user[U](user_class: Type[U]) -> U: @runtime_checkable class SupportsInt(Protocol): - """An ABC with one abstract method __int__.""" + """A protocol with one abstract method __int__.""" __slots__ = () @@ -2931,7 +2930,7 @@ def __int__(self) -> int: @runtime_checkable class SupportsFloat(Protocol): - """An ABC with one abstract method __float__.""" + """A protocol with one abstract method __float__.""" __slots__ = () @@ -2942,7 +2941,7 @@ def __float__(self) -> float: @runtime_checkable class SupportsComplex(Protocol): - """An ABC with one abstract method __complex__.""" + """A protocol with one abstract method __complex__.""" __slots__ = () @@ -2953,7 +2952,7 @@ def __complex__(self) -> complex: @runtime_checkable class SupportsBytes(Protocol): - """An ABC with one abstract method __bytes__.""" + """A protocol with one abstract method __bytes__.""" __slots__ = () @@ -2964,7 +2963,7 @@ def __bytes__(self) -> bytes: @runtime_checkable class SupportsIndex(Protocol): - """An ABC with one abstract method __index__.""" + """A protocol with one abstract method __index__.""" __slots__ = () @@ -2975,7 +2974,7 @@ def __index__(self) -> int: @runtime_checkable class SupportsAbs[T](Protocol): - """An ABC with one abstract method __abs__ that is covariant in its return type.""" + """A protocol with one abstract method __abs__ that is covariant in its return type.""" __slots__ = () @@ -2986,7 +2985,7 @@ def __abs__(self) -> T: @runtime_checkable class SupportsRound[T](Protocol): - """An ABC with one abstract method __round__ that is covariant in its return type.""" + """A protocol with one abstract method __round__ that is covariant in its return type.""" __slots__ = () @@ -3065,7 +3064,7 @@ def __new__(cls, typename, bases, ns): def NamedTuple(typename, fields=_sentinel, /, **kwargs): - """Typed version of namedtuple. + """Typed version of collections.namedtuple. Usage:: @@ -3077,8 +3076,8 @@ class Employee(NamedTuple): Employee = collections.namedtuple('Employee', ['name', 'id']) - The resulting class has an extra __annotations__ attribute, giving a - dict that maps field names to types. (The field names are also in + The types for each field name can be retrieved by calling + inspect.get_annotations(Employee). (The field names are also in the _fields attribute, which is part of the namedtuple API.) An alternative equivalent functional syntax is also accepted:: @@ -3163,7 +3162,7 @@ def __new__(cls, name, bases, ns, total=True): This method is called when TypedDict is subclassed, or when TypedDict is instantiated. This way - TypedDict supports all three syntax forms described in its docstring. + TypedDict classes can be created through both class-based and functional syntax. Subclasses and instances of TypedDict return actual dictionaries. """ for base in bases: @@ -3276,14 +3275,22 @@ def TypedDict(typename, fields=_sentinel, /, *, total=True): >>> Point2D(x=1, y=2, label='first') == dict(x=1, y=2, label='first') True - The type info can be accessed via the Point2D.__annotations__ dict, and - the Point2D.__required_keys__ and Point2D.__optional_keys__ frozensets. + The type info can be accessed by calling inspect.get_annotations(Point2D), and + via the Point2D.__required_keys__ and Point2D.__optional_keys__ frozensets. TypedDict supports an additional equivalent form:: Point2D = TypedDict('Point2D', {'x': int, 'y': int, 'label': str}) By default, all keys must be present in a TypedDict. It is possible - to override this by specifying totality:: + to override this by using the NotRequired and Required special forms:: + + class Point2D(TypedDict): + x: int # the "x" key must always be present (Required is the default) + y: NotRequired[int] # the "y" key can be omitted + + This means that a Point2D TypedDict can have the "y" key omitted, but the "x" key must be present. + Items are required by default, so the Required special form is not necessary in this example. + In addition, the total argument to the TypedDict function can be used to make all items not required:: class Point2D(TypedDict, total=False): x: int @@ -3292,16 +3299,8 @@ class Point2D(TypedDict, total=False): This means that a Point2D TypedDict can have any of the keys omitted. A type checker is only expected to support a literal False or True as the value of the total argument. True is the default, and makes all items defined in the - class body be required. - - The Required and NotRequired special forms can also be used to mark - individual keys as being required or not required:: - - class Point2D(TypedDict): - x: int # the "x" key must always be present (Required is the default) - y: NotRequired[int] # the "y" key can be omitted - - See PEP 655 for more details on Required and NotRequired. + class body be required. The Required special form can be used to mark individual + keys as required in a total=False TypedDict. The ReadOnly special form can be used to mark individual keys as immutable for type checkers:: @@ -3310,6 +3309,7 @@ class DatabaseUser(TypedDict): id: ReadOnly[int] # the "id" key must not be modified username: str # the "username" key can be changed + See PEPs 589, 655, and 705 for more information. """ if fields is _sentinel or fields is None: import warnings @@ -3356,7 +3356,7 @@ class Movie(TypedDict, total=False): year: int m = Movie( - title='The Matrix', # typechecker error if key is omitted + title='The Matrix', # type checker error if key is omitted year=1999, ) @@ -3378,7 +3378,7 @@ class Movie(TypedDict): year: NotRequired[int] m = Movie( - title='The Matrix', # typechecker error if key is omitted + title='The Matrix', # type checker error if key is omitted year=1999, ) """ @@ -3398,7 +3398,7 @@ class Movie(TypedDict): def mutate_movie(m: Movie) -> None: m["year"] = 1992 # allowed - m["title"] = "The Matrix" # typechecker error + m["title"] = "The Matrix" # type checker error There is no runtime checking for this property. """ @@ -3485,8 +3485,8 @@ class IO(Generic[AnyStr]): classes (text vs. binary, read vs. write vs. read/write, append-only, unbuffered). The TextIO and BinaryIO subclasses below capture the distinctions between text vs. binary, which is - pervasive in the interface; however we currently do not offer a - way to track the other distinctions in the type system. + pervasive in the interface. For more precise types, define a custom + Protocol. """ __slots__ = () @@ -3576,7 +3576,7 @@ def __exit__(self, type, value, traceback) -> None: class BinaryIO(IO[bytes]): - """Typed version of the return of open() in binary mode.""" + """Typed approximation of the return of open() in binary mode.""" __slots__ = () @@ -3590,7 +3590,7 @@ def __enter__(self) -> 'BinaryIO': class TextIO(IO[str]): - """Typed version of the return of open() in text mode.""" + """Typed approximation of the return of open() in text mode.""" __slots__ = () @@ -3657,7 +3657,7 @@ def dataclass_transform( field_specifiers: tuple[type[Any] | Callable[..., Any], ...] = (), **kwargs: Any, ) -> _IdentityCallable: - """Decorator to mark an object as providing dataclass-like behaviour. + """Decorator to mark an object as providing dataclass-like behavior. The decorator can be applied to a function, class, or metaclass. diff --git a/Misc/NEWS.d/next/Library/2026-05-18-07-44-46.gh-issue-149995.vvtFHn.rst b/Misc/NEWS.d/next/Library/2026-05-18-07-44-46.gh-issue-149995.vvtFHn.rst new file mode 100644 index 00000000000000..a8e412b578da37 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-05-18-07-44-46.gh-issue-149995.vvtFHn.rst @@ -0,0 +1 @@ +Update various docstrings in :mod:`typing`.