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gh-143658: Use str.lower and replace to further improve performance of importlib.metadata.Prepared.normalized #144083

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Merged
hugovk merged 1 commit into from
Feb 6, 2026
+6 −11
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gh-143658: Use str.lower and replace to further improve performance of importlib.metadata.Prepared.normalized #144083

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13 changes: 2 additions & 11 deletions Lib/importlib/metadata/__init__.py
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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 Down Expand Up @@ -933,9 +925,8 @@ def normalize(name):
"""
PEP 503 normalization plus dashes as underscores.
"""
# Emulates ``re.sub(r"[-_.]+", "-", name).lower()`` from PEP 503
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@jaraco jaraco Mar 20, 2026

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This change removes this important note that links the PEP 503 prescription from the actual implementation.

# 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
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@jaraco jaraco Mar 20, 2026

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This comment is now out of place. It's commenting on historical content.

value = name.lower().replace("-", "_").replace(".", "_")
# Condense repeats (faster than regex)
while "__" in value:
value = value.replace("__", "_")
Expand Down
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-01-20-20-54-46.gh-issue-143658.v8i1jE.rst
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@@ -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.
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