diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index c300c4257f0..c90cb411acd 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -616,6 +616,21 @@ These can be used as types in annotations and do not support ``[]``. avoiding type checker errors with classes that can duck type anywhere or are highly dynamic. +.. data:: AnyStr + + ``AnyStr`` is a :ref:`constrained type variable ` defined as + ``AnyStr = TypeVar('AnyStr', str, bytes)``. + + It is meant to be used for functions that may accept any kind of string + without allowing different kinds of strings to mix. For example:: + + def concat(a: AnyStr, b: AnyStr) -> AnyStr: + return a + b + + concat(u"foo", u"bar") # Ok, output has type 'unicode' + concat(b"foo", b"bar") # Ok, output has type 'bytes' + concat(u"foo", b"bar") # Error, cannot mix unicode and bytes + .. data:: LiteralString Special type that includes only literal strings. A string @@ -917,13 +932,13 @@ These can be used as types in annotations using ``[]``, each having a unique syn # We don't need to pass in the lock ourselves thanks to the decorator. sum_threadsafe([1.1, 2.2, 3.3]) -.. versionadded:: 3.10 + .. versionadded:: 3.10 -.. seealso:: + .. seealso:: - * :pep:`612` -- Parameter Specification Variables (the PEP which introduced - ``ParamSpec`` and ``Concatenate``). - * :class:`ParamSpec` and :class:`Callable`. + * :pep:`612` -- Parameter Specification Variables (the PEP which introduced + ``ParamSpec`` and ``Concatenate``). + * :class:`ParamSpec` and :class:`Callable`. .. class:: Type(Generic[CT_co]) @@ -1208,6 +1223,49 @@ These can be used as types in annotations using ``[]``, each having a unique syn .. versionadded:: 3.10 +.. data:: Unpack + + A typing operator that conceptually marks an object as having been + unpacked. For example, using the unpack operator ``*`` on a + :class:`type variable tuple ` is equivalent to using ``Unpack`` + to mark the type variable tuple as having been unpacked:: + + Ts = TypeVarTuple('Ts') + tup: tuple[*Ts] + # Effectively does: + tup: tuple[Unpack[Ts]] + + In fact, ``Unpack`` can be used interchangeably with ``*`` in the context + of :class:`typing.TypeVarTuple ` and + :class:`builtins.tuple ` types. You might see ``Unpack`` being used + explicitly in older versions of Python, where ``*`` couldn't be used in + certain places:: + + # In older versions of Python, TypeVarTuple and Unpack + # are located in the `typing_extensions` backports package. + from typing_extensions import TypeVarTuple, Unpack + + Ts = TypeVarTuple('Ts') + tup: tuple[*Ts] # Syntax error on Python <= 3.10! + tup: tuple[Unpack[Ts]] # Semantically equivalent, and backwards-compatible + + ``Unpack`` can also be used along with :class:`typing.TypedDict` for typing + ``**kwargs`` in a function signature:: + + from typing import TypedDict, Unpack + + class Movie(TypedDict): + name: str + year: int + + # This function expects two keyword arguments - `name` of type `str` + # and `year` of type `int`. + def foo(**kwargs: Unpack[Movie]): ... + + See :pep:`692` for more details on using ``Unpack`` for ``**kwargs`` typing. + + .. versionadded:: 3.11 + Building generic types """""""""""""""""""""" @@ -1409,49 +1467,6 @@ These are not used in annotations. They are building blocks for creating generic .. versionadded:: 3.11 -.. data:: Unpack - - A typing operator that conceptually marks an object as having been - unpacked. For example, using the unpack operator ``*`` on a - :class:`type variable tuple ` is equivalent to using ``Unpack`` - to mark the type variable tuple as having been unpacked:: - - Ts = TypeVarTuple('Ts') - tup: tuple[*Ts] - # Effectively does: - tup: tuple[Unpack[Ts]] - - In fact, ``Unpack`` can be used interchangeably with ``*`` in the context - of :class:`typing.TypeVarTuple ` and - :class:`builtins.tuple ` types. You might see ``Unpack`` being used - explicitly in older versions of Python, where ``*`` couldn't be used in - certain places:: - - # In older versions of Python, TypeVarTuple and Unpack - # are located in the `typing_extensions` backports package. - from typing_extensions import TypeVarTuple, Unpack - - Ts = TypeVarTuple('Ts') - tup: tuple[*Ts] # Syntax error on Python <= 3.10! - tup: tuple[Unpack[Ts]] # Semantically equivalent, and backwards-compatible - - ``Unpack`` can also be used along with :class:`typing.TypedDict` for typing - ``**kwargs`` in a function signature:: - - from typing import TypedDict, Unpack - - class Movie(TypedDict): - name: str - year: int - - # This function expects two keyword arguments - `name` of type `str` - # and `year` of type `int`. - def foo(**kwargs: Unpack[Movie]): ... - - See :pep:`692` for more details on using ``Unpack`` for ``**kwargs`` typing. - - .. versionadded:: 3.11 - .. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False) Parameter specification variable. A specialized version of @@ -1550,20 +1565,93 @@ These are not used in annotations. They are building blocks for creating generic .. versionadded:: 3.10 -.. data:: AnyStr +Other special directives +"""""""""""""""""""""""" - ``AnyStr`` is a :ref:`constrained type variable ` defined as - ``AnyStr = TypeVar('AnyStr', str, bytes)``. +These are not used in annotations. They are building blocks for declaring types. - It is meant to be used for functions that may accept any kind of string - without allowing different kinds of strings to mix. For example:: +.. class:: NamedTuple - def concat(a: AnyStr, b: AnyStr) -> AnyStr: - return a + b + Typed version of :func:`collections.namedtuple`. - concat(u"foo", u"bar") # Ok, output has type 'unicode' - concat(b"foo", b"bar") # Ok, output has type 'bytes' - concat(u"foo", b"bar") # Error, cannot mix unicode and bytes + Usage:: + + class Employee(NamedTuple): + name: str + id: int + + This is equivalent to:: + + Employee = collections.namedtuple('Employee', ['name', 'id']) + + To give a field a default value, you can assign to it in the class body:: + + class Employee(NamedTuple): + name: str + id: int = 3 + + employee = Employee('Guido') + assert employee.id == 3 + + 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 + ``_field_defaults`` attribute, both of which are part of the :func:`~collections.namedtuple` + API.) + + ``NamedTuple`` subclasses can also have docstrings and methods:: + + class Employee(NamedTuple): + """Represents an employee.""" + name: str + id: int = 3 + + def __repr__(self) -> str: + return f'' + + ``NamedTuple`` subclasses can be generic:: + + class Group(NamedTuple, Generic[T]): + key: T + group: list[T] + + Backward-compatible usage:: + + Employee = NamedTuple('Employee', [('name', str), ('id', int)]) + + .. versionchanged:: 3.6 + Added support for :pep:`526` variable annotation syntax. + + .. versionchanged:: 3.6.1 + Added support for default values, methods, and docstrings. + + .. versionchanged:: 3.8 + The ``_field_types`` and ``__annotations__`` attributes are + now regular dictionaries instead of instances of ``OrderedDict``. + + .. versionchanged:: 3.9 + Removed the ``_field_types`` attribute in favor of the more + standard ``__annotations__`` attribute which has the same information. + + .. versionchanged:: 3.11 + Added support for generic namedtuples. + +.. class:: NewType(name, tp) + + A helper class to indicate a distinct type to a typechecker, + see :ref:`distinct`. At runtime it returns an object that returns + its argument when called. + Usage:: + + UserId = NewType('UserId', int) + first_user = UserId(1) + + .. versionadded:: 3.5.2 + + .. versionchanged:: 3.10 + ``NewType`` is now a class rather than a function. .. class:: Protocol(Generic) @@ -1659,94 +1747,6 @@ These are not used in annotations. They are building blocks for creating generic for more details. -Other special directives -"""""""""""""""""""""""" - -These are not used in annotations. They are building blocks for declaring types. - -.. class:: NamedTuple - - Typed version of :func:`collections.namedtuple`. - - Usage:: - - class Employee(NamedTuple): - name: str - id: int - - This is equivalent to:: - - Employee = collections.namedtuple('Employee', ['name', 'id']) - - To give a field a default value, you can assign to it in the class body:: - - class Employee(NamedTuple): - name: str - id: int = 3 - - employee = Employee('Guido') - assert employee.id == 3 - - 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 - ``_field_defaults`` attribute, both of which are part of the :func:`~collections.namedtuple` - API.) - - ``NamedTuple`` subclasses can also have docstrings and methods:: - - class Employee(NamedTuple): - """Represents an employee.""" - name: str - id: int = 3 - - def __repr__(self) -> str: - return f'' - - ``NamedTuple`` subclasses can be generic:: - - class Group(NamedTuple, Generic[T]): - key: T - group: list[T] - - Backward-compatible usage:: - - Employee = NamedTuple('Employee', [('name', str), ('id', int)]) - - .. versionchanged:: 3.6 - Added support for :pep:`526` variable annotation syntax. - - .. versionchanged:: 3.6.1 - Added support for default values, methods, and docstrings. - - .. versionchanged:: 3.8 - The ``_field_types`` and ``__annotations__`` attributes are - now regular dictionaries instead of instances of ``OrderedDict``. - - .. versionchanged:: 3.9 - Removed the ``_field_types`` attribute in favor of the more - standard ``__annotations__`` attribute which has the same information. - - .. versionchanged:: 3.11 - Added support for generic namedtuples. - -.. class:: NewType(name, tp) - - A helper class to indicate a distinct type to a typechecker, - see :ref:`distinct`. At runtime it returns an object that returns - its argument when called. - Usage:: - - UserId = NewType('UserId', int) - first_user = UserId(1) - - .. versionadded:: 3.5.2 - - .. versionchanged:: 3.10 - ``NewType`` is now a class rather than a function. - .. class:: TypedDict(dict) Special construct to add type hints to a dictionary.