Sep 26, 2024 · May 21, 2024 · May 21, 2024 · May 21, 2024 · May 21, 2024 · May 21, 2024
diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst

   The :func:`partial` is used for partial function application which "freezes"
   some portion of a function's arguments and/or keywords resulting in a new object
   with a simplified signature.For example, :func:`partial` can be used to create
   with a simplified signature. For example, :func:`partial` can be used to create
   a callable that behaves like the :func:`int` function where the *base* argument
   defaults to two:

   when :func:`partial` is called. This allows custom selection of positional arguments
   to be pre-filled when constructing a :ref:`partial object <partial-objects>`.

   If :data:`!Placeholder` sentinels areused, all of them must be filled at call time:
   If :data:`!Placeholder` sentinels arepresent, all of them must be filled at call time:

      >>> from functools import partial, Placeholder
      >>> say_to_world = partial(print, Placeholder, Placeholder, "world!")
diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
 :meth:`!as_integer_ratio` method to a :class:`~fractions.Fraction`.
 (Contributed by Serhiy Storchaka in :gh:`82017`.)

 functools
 ---------

 * Added support to :func:`functools.partial` and
  :func:`functools.partialmethod` for :data:`functools.Placeholder` sentinels
  to reserve a place for positional arguments.
  (Contributed by Dominykas Grigonis in :gh:`119127`.)

 json
 ----

  to ``obj is not None``.
  (Contributed by Raymond Hettinger and Nico Mexis in :gh:`115808`.)

 functools
 ---------

 * :func:`functools.partial` and :func:`functools.partialmethod` now support
  :data:`functools.Placeholder` sentinels to reserve a place for
  positional arguments.
  (Contributed by Dominykas Grigonis in :gh:`119127`)

 os
 --

diff --git a/Lib/functools.py b/Lib/functools.py
 Placeholder = _PlaceholderType()

 def _partial_prepare_merger(args):
    nargs = len(args)
    if not nargs:
    if not args:
        return 0, None
    nargs = len(args)
    order = []
    j = nargs
    for i, a in enumerate(args):
    else:
        base_cls = partialmethod
        # func could be a descriptor like classmethod which isn't callable
        # assert issubclass(cls, partialmethod)
        if not callable(func) and not hasattr(func, "__get__"):
            raise TypeError(f"{func!r} is not callable or a descriptor")
            raise TypeError(f"the first argument {func!r} must be a callable "
                            "or a descriptor")
    if args and args[-1] is Placeholder:
        raise TypeError("trailing Placeholders are not allowed")
    if isinstance(func, base_cls):
                    args = args[phcount:]
                except IndexError:
                    raise TypeError("missing positional arguments "
                                    "in 'partial' call; expected "
                                    "in 'partialmethod' call; expected "
                                    f"at least {phcount}, got {len(args)}")
            else:
                pto_args = self.args
diff --git a/Lib/inspect.py b/Lib/inspect.py
                assert (not sig_params or
                        first_wrapped_param is not sig_params[0])
                # If there were placeholders set,
                #   first param istransformaed to positional only
                #   first param istransformed to positional only
                if partialmethod.args.count(functools.Placeholder):
                    first_wrapped_param = first_wrapped_param.replace(
                        kind=Parameter.POSITIONAL_ONLY)
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
        f = self.partial(signature)
        f.__setstate__((capture, (PH, 1), dict(a=10), dict(attr=[])))
        self.assertEqual(signature(f), (capture, (PH, 1), dict(a=10), dict(attr=[])))
        with self.assertRaises(TypeError):
        with self.assertRaises(TypeError) as cm:
            self.assertEqual(f(), (PH, 1), dict(a=10))
        expected = ("missing positional arguments in 'partial' call; "
                    "expected at least 1, got 0")
        self.assertEqual(cm.exception.args[0], expected)
        self.assertEqual(f(2), ((2, 1), dict(a=10)))

        #Leading Placeholder error
        #Trailing Placeholder error
        f = self.partial(signature)
        with self.assertRaises(TypeError):
        with self.assertRaises(TypeError) as cm:
            f.__setstate__((capture, (1, PH), dict(a=10), dict(attr=[])))
        expected = "trailing Placeholders are not allowed"
        self.assertEqual(cm.exception.args[0], expected)

    def test_setstate_errors(self):
        f = self.partial(signature)
    partial = PyPartialSubclass

    def test_subclass_optimization(self):
        # `partial` input to `partial` subclass
        p = py_functools.partial(min, 2)
        p2 = self.partial(p, 1)
        self.assertIs(p2.func, min)
        self.assertEqual(p2(0), 0)
        # `partial` subclass input to `partial` subclass
        p = self.partial(min, 2)
        p2 = self.partial(p, 1)
        self.assertIs(p2.func, min)
        self.assertEqual(p2(0), 0)


 class TestPartialMethod(unittest.TestCase):
    def test_subclass_optimization(self):
        class PartialMethodSubclass(functools.partialmethod):
            pass
        # `partialmethod` input to `partialmethod` subclass
        p = functools.partialmethod(min, 2)
        p2 = PartialMethodSubclass(p, 1)
        self.assertIs(p2.func, min)
        self.assertEqual(p2.__get__(0)(), 0)
        # `partialmethod` subclass input to `partialmethod` subclass
        p = PartialMethodSubclass(min, 2)
        p2 = PartialMethodSubclass(p, 1)
        self.assertIs(p2.func, min)
        self.assertEqual(p2.__get__(0)(), 0)


 class TestUpdateWrapper(unittest.TestCase):
Original file line number	Diff line number	Diff line change
Expand Up		@@ -348,7 +348,7 @@ The :mod:`functools` module defines the following functions:

		The :func:`partial` is used for partial function application which "freezes"
		some portion of a function's arguments and/or keywords resulting in a new object
		with a simplified signature.For example, :func:`partial` can be used to create
		with a simplified signature. For example, :func:`partial` can be used to create
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		a callable that behaves like the :func:`int` function where the base argument
		defaults to two:

Expand All		@@ -362,7 +362,7 @@ The :mod:`functools` module defines the following functions:
		when :func:`partial` is called. This allows custom selection of positional arguments
		to be pre-filled when constructing a :ref:`partial object <partial-objects>`.

		If :data:`!Placeholder` sentinels areused, all of them must be filled at call time:
		If :data:`!Placeholder` sentinels arepresent, all of them must be filled at call time:

		>>> from functools import partial, Placeholder
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		>>> say_to_world = partial(print, Placeholder, Placeholder, "world!")
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -117,6 +117,14 @@ Added support for converting any objects that have the
		:meth:`!as_integer_ratio` method to a :class:`~fractions.Fraction`.
		(Contributed by Serhiy Storchaka in :gh:`82017`.)

		functools
		---------

		* Added support to :func:`functools.partial` and
		:func:`functools.partialmethod` for :data:`functools.Placeholder` sentinels
		to reserve a place for positional arguments.
		(Contributed by Dominykas Grigonis in :gh:`119127`.)

		json
		----

Expand All		@@ -133,14 +141,6 @@ operator
		to ``obj is not None``.
		(Contributed by Raymond Hettinger and Nico Mexis in :gh:`115808`.)

		functools
		---------

		* :func:`functools.partial` and :func:`functools.partialmethod` now support
		:data:`functools.Placeholder` sentinels to reserve a place for
		positional arguments.
		(Contributed by Dominykas Grigonis in :gh:`119127`)

		os
		--

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -301,9 +301,9 @@ def __reduce__(self):
		Placeholder = _PlaceholderType()

		def _partial_prepare_merger(args):
		nargs = len(args)
		if not nargs:
		if not args:
		return 0, None
		nargs = len(args)
		order = []
		j = nargs
		for i, a in enumerate(args):
Expand All		@@ -324,9 +324,9 @@ def _partial_new(cls, func, /, args, *keywords):
		else:
		base_cls = partialmethod
		# func could be a descriptor like classmethod which isn't callable
		# assert issubclass(cls, partialmethod)
		if not callable(func) and not hasattr(func, "__get__"):
		raise TypeError(f"{func!r} is not callable or a descriptor")
		raise TypeError(f"the first argument {func!r} must be a callable "
		"or a descriptor")
		if args and args[-1] is Placeholder:
		raise TypeError("trailing Placeholders are not allowed")
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		if isinstance(func, base_cls):
Expand DownExpand Up		@@ -459,7 +459,7 @@ def _method(cls_or_self, /, args, *keywords):
		args = args[phcount:]
		except IndexError:
		raise TypeError("missing positional arguments "
		"in 'partial' call; expected "
		"in 'partialmethod' call; expected "
		f"at least {phcount}, got {len(args)}")
		else:
		pto_args = self.args
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2464,7 +2464,7 @@ def _signature_from_callable(obj, *,
		assert (not sig_params or
		first_wrapped_param is not sig_params[0])
		# If there were placeholders set,
		# first param istransformaed to positional only
		# first param istransformed to positional only
		if partialmethod.args.count(functools.Placeholder):
		first_wrapped_param = first_wrapped_param.replace(
		kind=Parameter.POSITIONAL_ONLY)
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -364,14 +364,19 @@ def test_setstate(self):
		f = self.partial(signature)
		f.__setstate__((capture, (PH, 1), dict(a=10), dict(attr=[])))
		self.assertEqual(signature(f), (capture, (PH, 1), dict(a=10), dict(attr=[])))
		with self.assertRaises(TypeError):
		with self.assertRaises(TypeError) as cm:
		self.assertEqual(f(), (PH, 1), dict(a=10))
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		expected = ("missing positional arguments in 'partial' call; "
		"expected at least 1, got 0")
		self.assertEqual(cm.exception.args[0], expected)
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		self.assertEqual(f(2), ((2, 1), dict(a=10)))

		#Leading Placeholder error
		#Trailing Placeholder error
		f = self.partial(signature)
		with self.assertRaises(TypeError):
		with self.assertRaises(TypeError) as cm:
		f.__setstate__((capture, (1, PH), dict(a=10), dict(attr=[])))
		expected = "trailing Placeholders are not allowed"
		self.assertEqual(cm.exception.args[0], expected)

		def test_setstate_errors(self):
		f = self.partial(signature)
Expand DownExpand Up		@@ -556,10 +561,16 @@ class TestPartialPySubclass(TestPartialPy):
		partial = PyPartialSubclass

		def test_subclass_optimization(self):
		# `partial` input to `partial` subclass
		p = py_functools.partial(min, 2)
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		p2 = self.partial(p, 1)
		self.assertIs(p2.func, min)
		self.assertEqual(p2(0), 0)
		# `partial` subclass input to `partial` subclass
		p = self.partial(min, 2)
		p2 = self.partial(p, 1)
		self.assertIs(p2.func, min)
		self.assertEqual(p2(0), 0)


		class TestPartialMethod(unittest.TestCase):
Expand DownExpand Up		@@ -702,10 +713,16 @@ def f(a, b, /):
		def test_subclass_optimization(self):
		class PartialMethodSubclass(functools.partialmethod):
		pass
		# `partialmethod` input to `partialmethod` subclass
		p = functools.partialmethod(min, 2)
		p2 = PartialMethodSubclass(p, 1)
		self.assertIs(p2.func, min)
		self.assertEqual(p2.__get__(0)(), 0)
		# `partialmethod` subclass input to `partialmethod` subclass
		p = PartialMethodSubclass(min, 2)
		p2 = PartialMethodSubclass(p, 1)
		self.assertIs(p2.func, min)
		self.assertEqual(p2.__get__(0)(), 0)


		class TestUpdateWrapper(unittest.TestCase):
Expand Down