gh-149083: Convert `_initial_missing` for pure py `reduce` to `sentinel` (#149536)

diff --git a/Lib/functools.py b/Lib/functools.py
index 73274b94ef37da0dfe2eb812206392e614c58528..409b2c50478c40fd9ec1bfd2b7256a45f301d517 100644 (file)
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -232,7 +232,7 @@ except ImportError:
 ### reduce() sequence to a single item
 ################################################################################
 
-_initial_missing = object()
+_initial_missing = sentinel('_initial_missing')
 
 def reduce(function, sequence, /, initial=_initial_missing):
     """