diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index e26a2226aa947a..93493614dac187 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -403,8 +403,7 @@ The :mod:`functools` module defines the following functions:
>>> remove_first_dear(message)
'Hello, dear world!'
- :data:`!Placeholder` has no special treatment when used in a keyword
- argument to :func:`!partial`.
+ :data:`!Placeholder` cannot be passed to :func:`!partial` as a keyword argument.
.. versionchanged:: 3.14
Added support for :data:`Placeholder` in positional arguments.
diff --git a/Lib/functools.py b/Lib/functools.py
index 9d53d3601559b2..d9550266771f51 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -326,6 +326,9 @@ def _partial_new(cls, func, /, *args, **keywords):
"or a descriptor")
if args and args[-1] is Placeholder:
raise TypeError("trailing Placeholders are not allowed")
+ for value in keywords.values():
+ if value is Placeholder:
+ raise TypeError("Placeholder cannot be passed as a keyword argument")
if isinstance(func, base_cls):
pto_phcount = func._phcount
tot_args = func.args
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index d590af090abc6e..eb5ee31fd16a3f 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -20,6 +20,7 @@
import contextlib
from inspect import Signature
+from test.support import ALWAYS_EQ
from test.support import import_helper
from test.support import threading_helper
@@ -233,6 +234,13 @@ def test_placeholders(self):
actual_args, actual_kwds = p('x', 'y')
self.assertEqual(actual_args, ('x', 0, 'y', 1))
self.assertEqual(actual_kwds, {})
+ # Checks via `is` and not `eq`
+ # thus ALWAYS_EQ isn't treated as Placeholder
+ p = self.partial(capture, ALWAYS_EQ)
+ actual_args, actual_kwds = p()
+ self.assertEqual(len(actual_args), 1)
+ self.assertIs(actual_args[0], ALWAYS_EQ)
+ self.assertEqual(actual_kwds, {})
def test_placeholders_optimization(self):
PH = self.module.Placeholder
@@ -249,6 +257,17 @@ def test_placeholders_optimization(self):
self.assertEqual(p2.args, (PH, 0))
self.assertEqual(p2(1), ((1, 0), {}))
+ def test_placeholders_kw_restriction(self):
+ PH = self.module.Placeholder
+ with self.assertRaisesRegex(TypeError, "Placeholder"):
+ self.partial(capture, a=PH)
+ # Passes, as checks via `is` and not `eq`
+ p = self.partial(capture, a=ALWAYS_EQ)
+ actual_args, actual_kwds = p()
+ self.assertEqual(actual_args, ())
+ self.assertEqual(len(actual_kwds), 1)
+ self.assertIs(actual_kwds['a'], ALWAYS_EQ)
+
def test_construct_placeholder_singleton(self):
PH = self.module.Placeholder
tp = type(PH)
diff --git a/Misc/NEWS.d/next/Library/2024-10-28-06-54-22.gh-issue-125028.GEY8Ws.rst b/Misc/NEWS.d/next/Library/2024-10-28-06-54-22.gh-issue-125028.GEY8Ws.rst
new file mode 100644
index 00000000000000..09ebee4d41b68e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-10-28-06-54-22.gh-issue-125028.GEY8Ws.rst
@@ -0,0 +1 @@
+:data:`functools.Placeholder` cannot be passed to :func:`functools.partial` as a keyword argument.
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index 802b1cf792c555..2db71fd864b006 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -196,6 +196,19 @@ partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
return NULL;
}
+ /* keyword Placeholder prohibition */
+ if (kw != NULL) {
+ PyObject *key, *val;
+ Py_ssize_t pos = 0;
+ while (PyDict_Next(kw, &pos, &key, &val)) {
+ if (val == phold) {
+ PyErr_SetString(PyExc_TypeError,
+ "Placeholder cannot be passed as a keyword argument");
+ return NULL;
+ }
+ }
+ }
+
/* check wrapped function / object */
pto_args = pto_kw = NULL;
int res = PyObject_TypeCheck(func, state->partial_type);
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