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bpo-47080: Use atomic groups to simplify fnmatch (GH-32029)

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Use re's new atomic groups to greatly simplify the construction of worst-case linear-time patterns.
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Tim Peters 2022-03-21 12:49:43 -05:00 • committed by GitHub
parent 345b390ed6
commit 5c3201e146
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2 changed files with 7 additions and 29 deletions
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12
Lib/test/test_fnmatch.py
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@ -124,17 +124,9 @@ class TranslateTestCase(unittest.TestCase):
self.assertEqual(translate('A*********?[?]?'), r'(?s:A.*.[?].)\Z')
# fancy translation to prevent exponential-time match failure
t = translate('**a*a****a')
digits = re.findall(r'\d+', t)
self.assertEqual(len(digits), 4)
self.assertEqual(digits[0], digits[1])
self.assertEqual(digits[2], digits[3])
g1 = f"g{digits[0]}" # e.g., group name "g4"
g2 = f"g{digits[2]}" # e.g., group name "g5"
self.assertEqual(t,
fr'(?s:(?=(?P<{g1}>.*?a))(?P={g1})(?=(?P<{g2}>.*?a))(?P={g2}).*a)\Z')
self.assertEqual(t, r'(?s:(?>.*?a)(?>.*?a).*a)\Z')
# and try pasting multiple translate results - it's an undocumented
# feature that this works; all the pain of generating unique group
# names across calls exists to support this
# feature that this works
r1 = translate('**a**a**a*')
r2 = translate('**b**b**b*')
r3 = translate('*c*c*c*')