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, default=<unrepresentable>)
 .. class:: TypeVar(name, *constraints, bound=None, covariant=False, contravariant=False, infer_variance=False, default=typing.NoDefault)

   Type variable.


 .. _typevartuple:

 .. class:: TypeVarTuple(name, default=<unrepresentable>)
 .. class:: TypeVarTuple(name, default=typing.NoDefault)

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

      Support for default values was added.

 .. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=<unrepresentable>)
 .. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=typing.NoDefault)

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

   .. versionadded:: 3.7.4

 .. data:: NoDefault

   A sentinel object used to represent the default value of certain parameters
   used in this module.

   .. versionadded:: 3.13

 Constant
 --------

diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
  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
 -----------

diff --git a/Include/internal/pycore_typevarobject.h b/Include/internal/pycore_typevarobject.h
 extern void _Py_clear_generic_types(PyInterpreterState *);

 extern PyTypeObject _PyTypeAlias_Type;
 extern PyObject _Py_NoDefaultStruct;

 #ifdef __cplusplus
 }
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
 from typing import Self, LiteralString
 from typing import TypeAlias
 from typing import ParamSpec, Concatenate, ParamSpecArgs, ParamSpecKwargs
 from typing import TypeGuard, TypeIs
 from typing import TypeGuard, TypeIs, NoDefault
 import abc
 import textwrap
 import typing
    def test_typevar_none(self):
        U = TypeVar('U')
        U_None = TypeVar('U_None', default=None)
        self.assertEqual(U.__default__, None)
        self.assertEqual(U_None.__default__, type(None))
        self.assertIs(U.__default__, NoDefault)
        self.assertIs(U_None.__default__, None)

        class X[T]: ...
        T, = X.__type_params__
        self.assertIs(T.__default__, NoDefault)

    def test_paramspec(self):
        P = ParamSpec('P', default=(str, int))
    def test_paramspec_none(self):
        U = ParamSpec('U')
        U_None = ParamSpec('U_None', default=None)
        self.assertEqual(U.__default__, None)
        self.assertEqual(U_None.__default__, type(None))
        self.assertIs(U.__default__, NoDefault)
        self.assertIs(U_None.__default__, None)

        class X[**P]: ...
        P, = X.__type_params__
        self.assertIs(P.__default__, NoDefault)

    def test_typevartuple(self):
        Ts = TypeVarTuple('Ts', default=Unpack[Tuple[str, int]])
    def test_typevartuple_none(self):
        U = TypeVarTuple('U')
        U_None = TypeVarTuple('U_None', default=None)
        self.assertEqual(U.__default__, None)
        self.assertEqual(U_None.__default__, type(None))
        self.assertIs(U.__default__, NoDefault)
        self.assertIs(U_None.__default__, None)

        class X[**Ts]: ...
        Ts, = X.__type_params__
        self.assertIs(Ts.__default__, NoDefault)

    def test_no_default_after_non_default(self):
        DefaultStrT = TypeVar('DefaultStrT', default=str)
        self.assertIsInstance(CustomerModel, Decorated)


 class NoDefaultTests(BaseTestCase):
    def test_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            s = pickle.dumps(NoDefault, proto)
            loaded = pickle.loads(s)
            self.assertIs(NoDefault, loaded)

    def test_constructor(self):
        self.assertIs(NoDefault, type(NoDefault)())
        with self.assertRaises(TypeError):
            NoDefault(1)

    def test_repr(self):
        self.assertEqual(repr(NoDefault), 'typing.NoDefault')

    def test_no_call(self):
        with self.assertRaises(TypeError):
            NoDefault()


 class AllTests(BaseTestCase):
    """Tests for __all__."""

diff --git a/Lib/typing.py b/Lib/typing.py
    ParamSpecKwargs,
    TypeAliasType,
    Generic,
    NoDefault,
 )

 # Please keep __all__ alphabetized within each category.
    'NewType',
    'no_type_check',
    'no_type_check_decorator',
    'NoDefault',
    'NoReturn',
    'NotRequired',
    'overload',
                        parameters.append(collected)
        elif hasattr(t, '__typing_subst__'):
            if t not in parameters:
                if type_var_tuple_encountered and t.__default__ is notNone:
                if type_var_tuple_encountered and t.__default__ is notNoDefault:
                    raise TypeError('Type parameter with a default'
                                    ' follows TypeVarTuple')

                if t.__default__ is notNone:
                if t.__default__ is notNoDefault:
                    default_encountered = True
                elif default_encountered:
                    raise TypeError(f'Type parameter {t!r} without a default'
            # the number of arguments being passed not matching the number
            # of parameters: all parameters that aren't explicitly
            # specialized in this call are parameters with default values.
            if cls.__parameters__[actual_len].__default__ is notNone:
            if cls.__parameters__[actual_len].__default__ is notNoDefault:
                return

            expected_len -= sum(p.__default__ is notNone for p in cls.__parameters__)
            expected_len -= sum(p.__default__ is notNoDefault for p in cls.__parameters__)
            expect_val = f"at least {expected_len}"
        else:
            expect_val = expected_len
    elif left + right > alen:
        raise TypeError(f"Too few arguments for {alias};"
                        f" actual {alen}, expected at least {plen-1}")
    if left == alen - right and self.__default__ is notNone:
    if left == alen - right and self.__default__ is notNoDefault:
        replacement = _unpack_args(self.__default__)
    else:
        replacement = args[left: alen - right]
 def _paramspec_prepare_subst(self, alias, args):
    params = alias.__parameters__
    i = params.index(self)
    if i == len(args) and self.__default__ is notNone:
    if i == len(args) and self.__default__ is notNoDefault:
        args = [*args, self.__default__]
    if i >= len(args):
        raise TypeError(f"Too few arguments for {alias}")
diff --git a/Modules/_typingmodule.c b/Modules/_typingmodule.c
    if (PyModule_AddObjectRef(m, "TypeAliasType", (PyObject *)&_PyTypeAlias_Type) < 0) {
        return -1;
    }
    if (PyModule_AddObjectRef(m, "NoDefault", (PyObject *)&_Py_NoDefaultStruct) < 0) {
        return -1;
    }
    return 0;
 }

diff --git a/Objects/clinic/typevarobject.c.h b/Objects/clinic/typevarobject.c.h
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, default=<unrepresentable>)
		.. class:: TypeVar(name, *constraints, bound=None, covariant=False, contravariant=False, infer_variance=False, default=typing.NoDefault)

		Type variable.

Expand DownExpand Up		@@ -1774,7 +1774,7 @@ without the dedicated syntax, as documented below.

		.. _typevartuple:

		.. class:: TypeVarTuple(name, default=<unrepresentable>)
		.. class:: TypeVarTuple(name, default=typing.NoDefault)

		Type variable tuple. A specialized form of :ref:`type variable <typevar>`
		that enables variadic generics.
Expand DownExpand Up		@@ -1903,7 +1903,7 @@ without the dedicated syntax, as documented below.

		Support for default values was added.

		.. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=<unrepresentable>)
		.. class:: ParamSpec(name, *, bound=None, covariant=False, contravariant=False, default=typing.NoDefault)

		Parameter specification variable. A specialized version of
		:ref:`type variables <typevar>`.
Expand DownExpand Up		@@ -3209,6 +3209,13 @@ Introspection helpers

		.. versionadded:: 3.7.4

		.. data:: NoDefault

		A sentinel object used to represent the default value of certain parameters
		used in this module.
JelleZijlstra marked this conversation as resolved. OutdatedShow resolvedHide resolved

		.. versionadded:: 3.13

		Constant
		--------

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -831,6 +831,10 @@ 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
		-----------

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -18,6 +18,7 @@ extern int _Py_initialize_generic(PyInterpreterState *);
		extern void _Py_clear_generic_types(PyInterpreterState *);

		extern PyTypeObject _PyTypeAlias_Type;
		extern PyObject _Py_NoDefaultStruct;

		#ifdef __cplusplus
		}
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -38,7 +38,7 @@
		from typing import Self, LiteralString
		from typing import TypeAlias
		from typing import ParamSpec, Concatenate, ParamSpecArgs, ParamSpecKwargs
		from typing import TypeGuard, TypeIs
		from typing import TypeGuard, TypeIs, NoDefault
		import abc
		import textwrap
		import typing
Expand DownExpand Up		@@ -592,8 +592,12 @@ class A(Generic[T]): ...
		def test_typevar_none(self):
		U = TypeVar('U')
		U_None = TypeVar('U_None', default=None)
		self.assertEqual(U.__default__, None)
		self.assertEqual(U_None.__default__, type(None))
		self.assertIs(U.__default__, NoDefault)
		self.assertIs(U_None.__default__, None)

		class X[T]: ...
		T, = X.__type_params__
		self.assertIs(T.__default__, NoDefault)

		def test_paramspec(self):
		P = ParamSpec('P', default=(str, int))
Expand All		@@ -609,8 +613,12 @@ class A(Generic[P]): ...
		def test_paramspec_none(self):
		U = ParamSpec('U')
		U_None = ParamSpec('U_None', default=None)
		self.assertEqual(U.__default__, None)
		self.assertEqual(U_None.__default__, type(None))
		self.assertIs(U.__default__, NoDefault)
		self.assertIs(U_None.__default__, None)

		class X[**P]: ...
		P, = X.__type_params__
		self.assertIs(P.__default__, NoDefault)

		def test_typevartuple(self):
		Ts = TypeVarTuple('Ts', default=Unpack[Tuple[str, int]])
Expand DownExpand Up		@@ -682,8 +690,12 @@ class A(Generic[T, P, U]): ...
		def test_typevartuple_none(self):
		U = TypeVarTuple('U')
		U_None = TypeVarTuple('U_None', default=None)
		self.assertEqual(U.__default__, None)
		self.assertEqual(U_None.__default__, type(None))
		self.assertIs(U.__default__, NoDefault)
		self.assertIs(U_None.__default__, None)

		class X[**Ts]: ...
		Ts, = X.__type_params__
		self.assertIs(Ts.__default__, NoDefault)

		def test_no_default_after_non_default(self):
		DefaultStrT = TypeVar('DefaultStrT', default=str)
Expand DownExpand Up		@@ -10145,6 +10157,26 @@ class CustomerModel(ModelBase, init=False):
		self.assertIsInstance(CustomerModel, Decorated)


		class NoDefaultTests(BaseTestCase):
		def test_pickling(self):
		for proto in range(pickle.HIGHEST_PROTOCOL + 1):
		s = pickle.dumps(NoDefault, proto)
		loaded = pickle.loads(s)
		self.assertIs(NoDefault, loaded)

		def test_constructor(self):
		self.assertIs(NoDefault, type(NoDefault)())
		with self.assertRaises(TypeError):
		NoDefault(1)

		def test_repr(self):
		self.assertEqual(repr(NoDefault), 'typing.NoDefault')

		def test_no_call(self):
		with self.assertRaises(TypeError):
		NoDefault()


		class AllTests(BaseTestCase):
		"""Tests for __all__."""

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -38,6 +38,7 @@
		ParamSpecKwargs,
		TypeAliasType,
		Generic,
		NoDefault,
		)

		# Please keep __all__ alphabetized within each category.
Expand DownExpand Up		@@ -138,6 +139,7 @@
		'NewType',
		'no_type_check',
		'no_type_check_decorator',
		'NoDefault',
		'NoReturn',
		'NotRequired',
		'overload',
Expand DownExpand Up		@@ -284,11 +286,11 @@ def _collect_parameters(args):
		parameters.append(collected)
		elif hasattr(t, '__typing_subst__'):
		if t not in parameters:
		if type_var_tuple_encountered and t.__default__ is notNone:
		if type_var_tuple_encountered and t.__default__ is notNoDefault:
		raise TypeError('Type parameter with a default'
		' follows TypeVarTuple')

		if t.__default__ is notNone:
		if t.__default__ is notNoDefault:
		default_encountered = True
		elif default_encountered:
		raise TypeError(f'Type parameter {t!r} without a default'
Expand DownExpand Up		@@ -323,10 +325,10 @@ def _check_generic_specialization(cls, arguments):
		# the number of arguments being passed not matching the number
		# of parameters: all parameters that aren't explicitly
		# specialized in this call are parameters with default values.
		if cls.__parameters__[actual_len].__default__ is notNone:
		if cls.__parameters__[actual_len].__default__ is notNoDefault:
		return

		expected_len -= sum(p.__default__ is notNone for p in cls.__parameters__)
		expected_len -= sum(p.__default__ is notNoDefault for p in cls.__parameters__)
		expect_val = f"at least {expected_len}"
		else:
		expect_val = expected_len
Expand DownExpand Up		@@ -1124,7 +1126,7 @@ def _typevartuple_prepare_subst(self, alias, args):
		elif left + right > alen:
		raise TypeError(f"Too few arguments for {alias};"
		f" actual {alen}, expected at least {plen-1}")
		if left == alen - right and self.__default__ is notNone:
		if left == alen - right and self.__default__ is notNoDefault:
		replacement = _unpack_args(self.__default__)
		else:
		replacement = args[left: alen - right]
Expand All		@@ -1150,7 +1152,7 @@ def _paramspec_subst(self, arg):
		def _paramspec_prepare_subst(self, alias, args):
		params = alias.__parameters__
		i = params.index(self)
		if i == len(args) and self.__default__ is notNone:
		if i == len(args) and self.__default__ is notNoDefault:
		args = [*args, self.__default__]
		if i >= len(args):
		raise TypeError(f"Too few arguments for {alias}")
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -63,6 +63,9 @@ _typing_exec(PyObject *m)
		if (PyModule_AddObjectRef(m, "TypeAliasType", (PyObject *)&_PyTypeAlias_Type) < 0) {
		return -1;
		}
		if (PyModule_AddObjectRef(m, "NoDefault", (PyObject *)&_Py_NoDefaultStruct) < 0) {
		return -1;
		}
		return 0;
		}

Expand Down