May 3, 2024 · Feb 29, 2024 · Feb 29, 2024 · Feb 29, 2024 · Feb 29, 2024 · Mar 1, 2024
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst

 .. _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=None)

   Type variable.

         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, if any.

      .. 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=None)

   Type variable tuple. A specialized form of :ref:`type variable <typevar>`
   that enables *variadic* generics.

      The name of the type variable tuple.

   .. attribute:: __default__

      The default value of the type variable, if any.

      .. versionadded:: 3.13

   .. versionadded:: 3.11

   .. versionchanged:: 3.12

      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=None)

   Parameter specification variable.  A specialized version of
   :ref:`type variables <typevar>`.

      The name of the parameter specification.

   .. attribute:: __default__

      The default value of the type variable, if any.

      .. 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
      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.
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst

 .. 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
 :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>`.

 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
 * 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 boundsandconstraintsfor typevariables
 * The bounds, constraints,anddefault valuesfor typeparameters
  (:ref:`lazily evaluated <lazy-evaluation>`).
 * The value of type aliases (:ref:`lazily evaluated <lazy-evaluation>`).

 .. versionadded:: 3.12
   Annotation scopes were introduced in Python 3.12 as part of :pep:`695`.

 .. versionchanged:: 3.13
   Annotation scopes are now 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 boundsandconstraints of type
 *lazily evaluated*. The same applies to the bounds, constraints,anddefault 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
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1616,7 +1616,7 @@ 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=None)
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		Type variable.

Expand DownExpand Up		@@ -1754,15 +1754,25 @@ 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, if any.

		.. 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=None)

		Type variable tuple. A specialized form of :ref:`type variable <typevar>`
		that enables variadic generics.
Expand DownExpand Up		@@ -1872,14 +1882,24 @@ without the dedicated syntax, as documented below.

		The name of the type variable tuple.

		.. attribute:: __default__

		The default value of the type variable, if any.

		.. versionadded:: 3.13

		.. versionadded:: 3.11

		.. versionchanged:: 3.12

		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=None)

		Parameter specification variable. A specialized version of
		:ref:`type variables <typevar>`.
Expand DownExpand Up		@@ -1948,6 +1968,12 @@ without the dedicated syntax, as documented below.

		The name of the parameter specification.

		.. attribute:: __default__

		The default value of the type variable, if any.

		.. 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
Expand All		@@ -1961,6 +1987,10 @@ 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.
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -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
Expand DownExpand Up		@@ -1694,19 +1697,29 @@ 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>`.
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		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:
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -204,7 +204,7 @@ 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 boundsandconstraintsfor typevariables
		* The bounds, constraints,anddefault valuesfor typeparameters
		(:ref:`lazily evaluated <lazy-evaluation>`).
		* The value of type aliases (:ref:`lazily evaluated <lazy-evaluation>`).

Expand All		@@ -231,13 +231,17 @@ 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 now also used for type parameter defaults, as
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		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 boundsandconstraints of type
		lazily evaluated. The same applies to the bounds, constraints,anddefault 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
Expand Down