https://github.com/python/cpython/commit/51e0f2b06c042b8742145ce094323a34b61f02aa
commit: 51e0f2b06c042b8742145ce094323a34b61f02aa
branch: main
author: Adam Turner <9087854+aa-tur...@users.noreply.github.com>
committer: AA-Turner <9087854+aa-tur...@users.noreply.github.com>
date: 2025-03-31T18:31:39+01:00
summary:
gh-107369: Optimise ``textwrap.indent()`` (#131923)
Co-authored-by: Bénédikt Tran <10796600+picn...@users.noreply.github.com>
files:
A Misc/NEWS.d/next/Library/2025-03-31-02-06-57.gh-issue-107369.8M-HVz.rst
M Lib/textwrap.py
diff --git a/Lib/textwrap.py b/Lib/textwrap.py
index bb6a1186316275..bac98c99e41df8 100644
--- a/Lib/textwrap.py
+++ b/Lib/textwrap.py
@@ -451,19 +451,20 @@ def indent(text, prefix, predicate=None):
it will default to adding 'prefix' to all non-empty lines that do not
consist solely of whitespace characters.
"""
- if predicate is None:
- # str.splitlines(True) doesn't produce empty string.
- # ''.splitlines(True) => []
- # 'foo\n'.splitlines(True) => ['foo\n']
- # So we can use just `not s.isspace()` here.
- predicate = lambda s: not s.isspace()
-
prefixed_lines = []
- for line in text.splitlines(True):
- if predicate(line):
- prefixed_lines.append(prefix)
- prefixed_lines.append(line)
-
+ if predicate is None:
+ # str.splitlines(keepends=True) doesn't produce the empty string,
+ # so we need to use `str.isspace()` rather than a truth test.
+ # Inlining the predicate leads to a ~30% performance improvement.
+ for line in text.splitlines(True):
+ if not line.isspace():
+ prefixed_lines.append(prefix)
+ prefixed_lines.append(line)
+ else:
+ for line in text.splitlines(True):
+ if predicate(line):
+ prefixed_lines.append(prefix)
+ prefixed_lines.append(line)
return ''.join(prefixed_lines)
diff --git
a/Misc/NEWS.d/next/Library/2025-03-31-02-06-57.gh-issue-107369.8M-HVz.rst
b/Misc/NEWS.d/next/Library/2025-03-31-02-06-57.gh-issue-107369.8M-HVz.rst
new file mode 100644
index 00000000000000..9b1bd9e7502bf0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-03-31-02-06-57.gh-issue-107369.8M-HVz.rst
@@ -0,0 +1,2 @@
+Improved performance of :func:`textwrap.dedent` by an average of ~1.3x.
+Patch by Adam Turner.
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