https://github.com/python/cpython/commit/bce45bcaf88c579c6fffcc4b20147d60caca5364
commit: bce45bcaf88c579c6fffcc4b20147d60caca5364
branch: main
author: Semyon Moroz <donbar...@proton.me>
committer: AA-Turner <9087854+aa-tur...@users.noreply.github.com>
date: 2025-05-01T04:11:36Z
summary:
gh-130167: Improve ``difflib.IS_LINE_JUNK`` performance by using string methods
(#130170)
Co-authored-by: Adam Turner <9087854+aa-tur...@users.noreply.github.com>
Co-authored-by: Bénédikt Tran <10796600+picn...@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hug...@users.noreply.github.com>
Co-authored-by: Tim Peters <tim.pet...@gmail.com>
files:
A Misc/NEWS.d/next/Library/2025-02-16-06-25-01.gh-issue-130167.kUg7Rc.rst
M Lib/difflib.py
diff --git a/Lib/difflib.py b/Lib/difflib.py
index 4bba9e7ea5cfa8..f1f4e62514a7bd 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -1038,11 +1038,9 @@ def _qformat(self, aline, bline, atags, btags):
# remaining is that perhaps it was really the case that " volatile"
# was inserted after "private". I can live with that <wink>.
-import re
-
-def IS_LINE_JUNK(line, pat=re.compile(r"\s*(?:#\s*)?$").match):
+def IS_LINE_JUNK(line, pat=None):
r"""
- Return True for ignorable line: iff `line` is blank or contains a single
'#'.
+ Return True for ignorable line: if `line` is blank or contains a single
'#'.
Examples:
@@ -1054,6 +1052,11 @@ def IS_LINE_JUNK(line,
pat=re.compile(r"\s*(?:#\s*)?$").match):
False
"""
+ if pat is None:
+ # Default: match '#' or the empty string
+ return line.strip() in '#'
+ # Previous versions used the undocumented parameter 'pat' as a
+ # match function. Retain this behaviour for compatibility.
return pat(line) is not None
def IS_CHARACTER_JUNK(ch, ws=" \t"):
@@ -2027,7 +2030,6 @@ def
make_table(self,fromlines,tolines,fromdesc='',todesc='',context=False,
replace('\1','</span>'). \
replace('\t',' ')
-del re
def restore(delta, which):
r"""
diff --git
a/Misc/NEWS.d/next/Library/2025-02-16-06-25-01.gh-issue-130167.kUg7Rc.rst
b/Misc/NEWS.d/next/Library/2025-02-16-06-25-01.gh-issue-130167.kUg7Rc.rst
new file mode 100644
index 00000000000000..3d397084fc136c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-02-16-06-25-01.gh-issue-130167.kUg7Rc.rst
@@ -0,0 +1 @@
+Improve speed of :func:`difflib.IS_LINE_JUNK`. Patch by Semyon Moroz.
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