From b03a69e5bc1cda4fd225fb965b387dd8d4a609bd Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <raymond.hettinger@gmail.com>
Date: Sat, 31 Oct 2026 15:23:32 -0500
Subject: [PATCH 1/2] Simplify Placeholder with the new sentinel() class

---
 Lib/functools.py           | 24 +-----------------------
 Lib/test/test_functools.py |  7 -------
 2 files changed, 1 insertion(+), 30 deletions(-)

diff --git a/Lib/functools.py b/Lib/functools.py
index 2c08791d4d2651b..1679b67b1300721 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -275,29 +275,7 @@ def reduce(function, sequence, /, initial=_initial_missing):
 ################################################################################
 
 
-class _PlaceholderType:
-    """The type of the Placeholder singleton.
-
-    Used as a placeholder for partial arguments.
-    """
-    __instance = None
-    __slots__ = ()
-
-    def __init_subclass__(cls, *args, **kwargs):
-        raise TypeError(f"type '{cls.__name__}' is not an acceptable base type")
-
-    def __new__(cls):
-        if cls.__instance is None:
-            cls.__instance = object.__new__(cls)
-        return cls.__instance
-
-    def __repr__(self):
-        return 'Placeholder'
-
-    def __reduce__(self):
-        return 'Placeholder'
-
-Placeholder = _PlaceholderType()
+Placeholder = sentinel('Placeholder') # _PlaceholderType()
 
 def _partial_prepare_merger(args):
     if not args:
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index 6aa7916adc0bb86..0eb5efcb6e18e26 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -279,13 +279,6 @@ def test_placeholders_kw_restriction(self):
         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)
-        self.assertIs(tp(), PH)
-        self.assertRaises(TypeError, tp, 1, 2)
-        self.assertRaises(TypeError, tp, a=1, b=2)
-
     def test_repr(self):
         args = (object(), object())
         args_repr = ', '.join(repr(a) for a in args)

From 4f77a8c9859f5daddba37e14eaedba87080a5c48 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <raymond.hettinger@gmail.com>
Date: Sat, 31 Oct 2026 15:32:43 -0500
Subject: [PATCH 2/2] Remove unused import

---
 Lib/functools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/functools.py b/Lib/functools.py
index 1679b67b1300721..05993163506ac52 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -418,7 +418,7 @@ def __setstate__(self, state):
 
 
 try:
-    from _functools import partial, Placeholder, _PlaceholderType
+    from _functools import partial, Placeholder
 except ImportError:
     pass