diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/library/ast.rst | 52 | ||||
| -rw-r--r-- | Doc/library/typing.rst | 82 | ||||
| -rw-r--r-- | Doc/reference/compound_stmts.rst | 31 | ||||
| -rw-r--r-- | Doc/reference/executionmodel.rst | 8 | ||||
| -rw-r--r-- | Doc/whatsnew/3.13.rst | 6 |
5 files changed, 152 insertions, 27 deletions
diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst index 09f2a40..e954c38 100644 --- a/Doc/library/ast.rst +++ b/Doc/library/ast.rst @@ -1748,15 +1748,17 @@ Type parameters :ref:`Type parameters <type-params>` can exist on classes, functions, and type aliases. -.. class:: TypeVar(name, bound) +.. class:: TypeVar(name, bound, default_value) - A :class:`typing.TypeVar`. ``name`` is the name of the type variable. - ``bound`` is the bound or constraints, if any. If ``bound`` is a :class:`Tuple`, - it represents constraints; otherwise it represents the bound. + A :class:`typing.TypeVar`. *name* is the name of the type variable. + *bound* is the bound or constraints, if any. If *bound* is a :class:`Tuple`, + it represents constraints; otherwise it represents the bound. *default_value* + is the default value; if the :class:`!TypeVar` has no default, this + attribute will be set to ``None``. .. doctest:: - >>> print(ast.dump(ast.parse("type Alias[T: int] = list[T]"), indent=4)) + >>> print(ast.dump(ast.parse("type Alias[T: int = bool] = list[T]"), indent=4)) Module( body=[ TypeAlias( @@ -1764,7 +1766,8 @@ aliases. type_params=[ TypeVar( name='T', - bound=Name(id='int', ctx=Load()))], + bound=Name(id='int', ctx=Load()), + default_value=Name(id='bool', ctx=Load()))], value=Subscript( value=Name(id='list', ctx=Load()), slice=Name(id='T', ctx=Load()), @@ -1772,19 +1775,30 @@ aliases. .. versionadded:: 3.12 -.. class:: ParamSpec(name) + .. versionchanged:: 3.13 + Added the *default_value* parameter. + +.. class:: ParamSpec(name, default_value) - A :class:`typing.ParamSpec`. ``name`` is the name of the parameter specification. + A :class:`typing.ParamSpec`. *name* is the name of the parameter specification. + *default_value* is the default value; if the :class:`!ParamSpec` has no default, + this attribute will be set to ``None``. .. doctest:: - >>> print(ast.dump(ast.parse("type Alias[**P] = Callable[P, int]"), indent=4)) + >>> print(ast.dump(ast.parse("type Alias[**P = (int, str)] = Callable[P, int]"), indent=4)) Module( body=[ TypeAlias( name=Name(id='Alias', ctx=Store()), type_params=[ - ParamSpec(name='P')], + ParamSpec( + name='P', + default_value=Tuple( + elts=[ + Name(id='int', ctx=Load()), + Name(id='str', ctx=Load())], + ctx=Load()))], value=Subscript( value=Name(id='Callable', ctx=Load()), slice=Tuple( @@ -1796,19 +1810,26 @@ aliases. .. versionadded:: 3.12 -.. class:: TypeVarTuple(name) + .. versionchanged:: 3.13 + Added the *default_value* parameter. + +.. class:: TypeVarTuple(name, default_value) - A :class:`typing.TypeVarTuple`. ``name`` is the name of the type variable tuple. + A :class:`typing.TypeVarTuple`. *name* is the name of the type variable tuple. + *default_value* is the default value; if the :class:`!TypeVarTuple` has no + default, this attribute will be set to ``None``. .. doctest:: - >>> print(ast.dump(ast.parse("type Alias[*Ts] = tuple[*Ts]"), indent=4)) + >>> print(ast.dump(ast.parse("type Alias[*Ts = ()] = tuple[*Ts]"), indent=4)) Module( body=[ TypeAlias( name=Name(id='Alias', ctx=Store()), type_params=[ - TypeVarTuple(name='Ts')], + TypeVarTuple( + name='Ts', + default_value=Tuple(ctx=Load()))], value=Subscript( value=Name(id='tuple', ctx=Load()), slice=Tuple( @@ -1821,6 +1842,9 @@ aliases. .. versionadded:: 3.12 + .. versionchanged:: 3.13 + Added the *default_value* parameter. + Function and class definitions ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst index 573318b..e062872 100644 --- a/Doc/library/typing.rst +++ b/Doc/library/typing.rst @@ -1614,7 +1614,7 @@ without the dedicated syntax, as documented below. .. _typevar: -.. class:: TypeVar(name, *constraints, bound=None, covariant=False, contravariant=False, infer_variance=False) +.. class:: TypeVar(name, *constraints, bound=None, covariant=False, contravariant=False, infer_variance=False, default=typing.NoDefault) Type variable. @@ -1752,15 +1752,35 @@ without the dedicated syntax, as documented below. the constraints are evaluated only when the attribute is accessed, not when the type variable is created (see :ref:`lazy-evaluation`). + .. attribute:: __default__ + + The default value of the type variable, or :data:`typing.NoDefault` if it + has no default. + + .. versionadded:: 3.13 + + .. method:: has_default() + + Return whether or not the type variable has a default value. This is equivalent + to checking whether :attr:`__default__` is not the :data:`typing.NoDefault` + singleton, except that it does not force evaluation of the + :ref:`lazily evaluated <lazy-evaluation>` default value. + + .. versionadded:: 3.13 + .. versionchanged:: 3.12 Type variables can now be declared using the :ref:`type parameter <type-params>` syntax introduced by :pep:`695`. The ``infer_variance`` parameter was added. + .. versionchanged:: 3.13 + + Support for default values was added. + .. _typevartuple: -.. class:: TypeVarTuple(name) +.. class:: TypeVarTuple(name, default=typing.NoDefault) Type variable tuple. A specialized form of :ref:`type variable <typevar>` that enables *variadic* generics. @@ -1870,6 +1890,22 @@ without the dedicated syntax, as documented below. The name of the type variable tuple. + .. attribute:: __default__ + + The default value of the type variable tuple, or :data:`typing.NoDefault` if it + has no default. + + .. versionadded:: 3.13 + + .. method:: has_default() + + Return whether or not the type variable tuple has a default value. This is equivalent + to checking whether :attr:`__default__` is not the :data:`typing.NoDefault` + singleton, except that it does not force evaluation of the + :ref:`lazily evaluated <lazy-evaluation>` default value. + + .. versionadded:: 3.13 + .. versionadded:: 3.11 .. versionchanged:: 3.12 @@ -1877,7 +1913,11 @@ without the dedicated syntax, as documented below. Type variable tuples can now be declared using the :ref:`type parameter <type-params>` syntax introduced by :pep:`695`. -.. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False) + .. versionchanged:: 3.13 + + Support for default values was added. + +.. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=typing.NoDefault) Parameter specification variable. A specialized version of :ref:`type variables <typevar>`. @@ -1946,6 +1986,22 @@ without the dedicated syntax, as documented below. The name of the parameter specification. + .. attribute:: __default__ + + The default value of the parameter specification, or :data:`typing.NoDefault` if it + has no default. + + .. versionadded:: 3.13 + + .. method:: has_default() + + Return whether or not the parameter specification has a default value. This is equivalent + to checking whether :attr:`__default__` is not the :data:`typing.NoDefault` + singleton, except that it does not force evaluation of the + :ref:`lazily evaluated <lazy-evaluation>` default value. + + .. versionadded:: 3.13 + Parameter specification variables created with ``covariant=True`` or ``contravariant=True`` can be used to declare covariant or contravariant generic types. The ``bound`` argument is also accepted, similar to @@ -1959,6 +2015,10 @@ without the dedicated syntax, as documented below. Parameter specifications can now be declared using the :ref:`type parameter <type-params>` syntax introduced by :pep:`695`. + .. versionchanged:: 3.13 + + Support for default values was added. + .. note:: Only parameter specification variables defined in global scope can be pickled. @@ -3171,6 +3231,22 @@ Introspection helpers .. versionadded:: 3.7.4 +.. data:: NoDefault + + A sentinel object used to indicate that a type parameter has no default + value. For example: + + .. doctest:: + + >>> T = TypeVar("T") + >>> T.__default__ is typing.NoDefault + True + >>> S = TypeVar("S", default=None) + >>> S.__default__ is None + True + + .. versionadded:: 3.13 + Constant -------- diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst index 374404b..42cca06 100644 --- a/Doc/reference/compound_stmts.rst +++ b/Doc/reference/compound_stmts.rst @@ -1620,15 +1620,18 @@ Type parameter lists .. versionadded:: 3.12 +.. versionchanged:: 3.13 + Support for default values was added (see :pep:`696`). + .. index:: single: type parameters .. productionlist:: python-grammar type_params: "[" `type_param` ("," `type_param`)* "]" type_param: `typevar` | `typevartuple` | `paramspec` - typevar: `identifier` (":" `expression`)? - typevartuple: "*" `identifier` - paramspec: "**" `identifier` + typevar: `identifier` (":" `expression`)? ("=" `expression`)? + typevartuple: "*" `identifier` ("=" `expression`)? + paramspec: "**" `identifier` ("=" `expression`)? :ref:`Functions <def>` (including :ref:`coroutines <async def>`), :ref:`classes <class>` and :ref:`type aliases <type>` may @@ -1694,19 +1697,31 @@ evaluated in a separate :ref:`annotation scope <annotation-scopes>`. :data:`typing.TypeVarTuple`\ s and :data:`typing.ParamSpec`\ s cannot have bounds or constraints. +All three flavors of type parameters can also have a *default value*, which is used +when the type parameter is not explicitly provided. This is added by appending +a single equals sign (``=``) followed by an expression. Like the bounds and +constraints of type variables, the default value is not evaluated when the +object is created, but only when the type parameter's ``__default__`` attribute +is accessed. To this end, the default value is evaluated in a separate +:ref:`annotation scope <annotation-scopes>`. If no default value is specified +for a type parameter, the ``__default__`` attribute is set to the special +sentinel object :data:`typing.NoDefault`. + The following example indicates the full set of allowed type parameter declarations:: def overly_generic[ SimpleTypeVar, + TypeVarWithDefault = int, TypeVarWithBound: int, TypeVarWithConstraints: (str, bytes), - *SimpleTypeVarTuple, - **SimpleParamSpec, + *SimpleTypeVarTuple = (int, float), + **SimpleParamSpec = (str, bytearray), ]( a: SimpleTypeVar, - b: TypeVarWithBound, - c: Callable[SimpleParamSpec, TypeVarWithConstraints], - *d: SimpleTypeVarTuple, + b: TypeVarWithDefault, + c: TypeVarWithBound, + d: Callable[SimpleParamSpec, TypeVarWithConstraints], + *e: SimpleTypeVarTuple, ): ... .. _generic-functions: diff --git a/Doc/reference/executionmodel.rst b/Doc/reference/executionmodel.rst index ed50fae..f24e153 100644 --- a/Doc/reference/executionmodel.rst +++ b/Doc/reference/executionmodel.rst @@ -205,7 +205,7 @@ Annotation scopes are used in the following contexts: * Type parameter lists for :ref:`generic classes <generic-classes>`. A generic class's base classes and keyword arguments are executed within the annotation scope, but its decorators are not. -* The bounds and constraints for type variables +* The bounds, constraints, and default values for type parameters (:ref:`lazily evaluated <lazy-evaluation>`). * The value of type aliases (:ref:`lazily evaluated <lazy-evaluation>`). @@ -232,13 +232,17 @@ Annotation scopes differ from function scopes in the following ways: .. versionadded:: 3.12 Annotation scopes were introduced in Python 3.12 as part of :pep:`695`. +.. versionchanged:: 3.13 + Annotation scopes are also used for type parameter defaults, as + introduced by :pep:`696`. + .. _lazy-evaluation: Lazy evaluation --------------- The values of type aliases created through the :keyword:`type` statement are -*lazily evaluated*. The same applies to the bounds and constraints of type +*lazily evaluated*. The same applies to the bounds, constraints, and default values of type variables created through the :ref:`type parameter syntax <type-params>`. This means that they are not evaluated when the type alias or type variable is created. Instead, they are only evaluated when doing so is necessary to resolve diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst index d59c4ee..d996cf6 100644 --- a/Doc/whatsnew/3.13.rst +++ b/Doc/whatsnew/3.13.rst @@ -89,6 +89,8 @@ Interpreter improvements: New typing features: +* :pep:`696`: Type parameters (:data:`typing.TypeVar`, :data:`typing.ParamSpec`, + and :data:`typing.TypeVarTuple`) now support defaults. * :pep:`742`: :data:`typing.TypeIs` was added, providing more intuitive type narrowing behavior. @@ -850,6 +852,10 @@ typing an item of a :class:`typing.TypedDict` as read-only for type checkers. See :pep:`705` for more details. +* Add :data:`typing.NoDefault`, a sentinel object used to represent the defaults + of some parameters in the :mod:`typing` module. (Contributed by Jelle Zijlstra in + :gh:`116126`.) + unicodedata ----------- |