Jan 20, 2026
diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
        return itertools.chain(infos, eggs)


 # Translation table for Prepared.normalize: lowercase and
 # replace "-" (hyphen) and "." (dot) with "_" (underscore).
 _normalize_table = str.maketrans(
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ-.",
    "abcdefghijklmnopqrstuvwxyz__",
 )


 class Prepared:
    """
    A prepared search query for metadata on a possibly-named package.
        """
        PEP 503 normalization plus dashes as underscores.
        """
        # Emulates ``re.sub(r"[-_.]+", "-", name).lower()`` from PEP 503
        # About 3x faster, safe since packages only support alphanumeric characters
        value = name.translate(_normalize_table)
        # Much faster than re.sub, and even faster than str.translate
        value = name.lower().replace("-", "_").replace(".", "_")
        # Condense repeats (faster than regex)
        while "__" in value:
            value = value.replace("__", "_")
diff --git a/Misc/NEWS.d/next/Library/2026-01-20-20-54-46.gh-issue-143658.v8i1jE.rst b/Misc/NEWS.d/next/Library/2026-01-20-20-54-46.gh-issue-143658.v8i1jE.rst
 :mod:`importlib.metadata`: Use :meth:`str.lower` and :meth:`str.replace` to
 further improve performance of
 :meth:`!importlib.metadata.Prepared.normalize`. Patch by Hugo van Kemenade
 and Henry Schreiner.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -890,14 +890,6 @@ def search(self, prepared: Prepared):
		return itertools.chain(infos, eggs)


		# Translation table for Prepared.normalize: lowercase and
		# replace "-" (hyphen) and "." (dot) with "_" (underscore).
		_normalize_table = str.maketrans(
		"ABCDEFGHIJKLMNOPQRSTUVWXYZ-.",
		"abcdefghijklmnopqrstuvwxyz__",
		)


		class Prepared:
		"""
		A prepared search query for metadata on a possibly-named package.
Expand DownExpand Up		@@ -933,9 +925,8 @@ def normalize(name):
		"""
		PEP 503 normalization plus dashes as underscores.
		"""
		# Emulates ``re.sub(r"[-_.]+", "-", name).lower()`` from PEP 503
		# About 3x faster, safe since packages only support alphanumeric characters
		value = name.translate(_normalize_table)
		# Much faster than re.sub, and even faster than str.translate
		value = name.lower().replace("-", "_").replace(".", "_")
		# Condense repeats (faster than regex)
		while "__" in value:
		value = value.replace("__", "_")
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,4 @@
		:mod:`importlib.metadata`: Use :meth:`str.lower` and :meth:`str.replace` to
		further improve performance of
		:meth:`!importlib.metadata.Prepared.normalize`. Patch by Hugo van Kemenade
		and Henry Schreiner.