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 +1052,7 @@ def IS_LINE_JUNK(line, pat=re.compile(r"\s*(?:#\s*)?$").match):
     False
     """
 
-    return pat(line) is not None
+    return line.strip() in ('', '#')
 
 def IS_CHARACTER_JUNK(ch, ws=" \t"):
     r"""
@@ -2027,7 +2025,6 @@ 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 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.