python · AA-Turner · May 1, 2025 · Feb 16, 2025 · Feb 16, 2025 · Feb 16, 2025
diff --git a/Lib/difflib.py b/Lib/difflib.py
@@ -1038,9 +1038,7 @@ 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 '#'.

@@ -1054,7 +1052,9 @@ def IS_LINE_JUNK(line, pat=re.compile(r"\s*(?:#\s*)?$").match):
    False
    """

-    return pat(line) is not None
+    return (line.strip() in ('', '#')
+            if pat is None
+            else pat(line) is not None)

 def IS_CHARACTER_JUNK(ch, ws=" \t"):
    r"""
@@ -2027,7 +2027,6 @@ def make_table(self,fromlines,tolines,fromdesc='',todesc='',context=False,
                     replace('\1','</span>'). \
                     replace('\t','&nbsp;')

-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
@@ -0,0 +1,2 @@
+Improve speed of :func:`difflib.IS_LINE_JUNK` by replacing :mod:`re` with
+built-in string methods.
-Original file line number
+Diff line change
@@ -0,0 +1,2 @@
+    Improve speed of :func:`difflib.IS_LINE_JUNK` by replacing :mod:`re` with
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+    built-in string methods.