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Fix SF bug #763023, difflib.py: ratio() zero division not caught

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Backport candidate
This commit is contained in:
Neal Norwitz 2003-07-01 14:59:46 +00:00
parent 37ca8c12dc
commit e7dfe21bed
3 changed files with 23 additions and 3 deletions
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11
Lib/difflib.py
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@ -29,6 +29,11 @@ __all__ = ['get_close_matches', 'ndiff', 'restore', 'SequenceMatcher',
'Differ','IS_CHARACTER_JUNK', 'IS_LINE_JUNK', 'context_diff',
'unified_diff']
def _calculate_ratio(matches, length):
if length:
return 2.0 * matches / length
return 1.0
class SequenceMatcher:
"""
@ -611,7 +616,7 @@ class SequenceMatcher:
matches = reduce(lambda sum, triple: sum + triple[-1],
self.get_matching_blocks(), 0)
return 2.0 * matches / (len(self.a) + len(self.b))
return _calculate_ratio(matches, len(self.a) + len(self.b))
def quick_ratio(self):
"""Return an upper bound on ratio() relatively quickly.
@ -640,7 +645,7 @@ class SequenceMatcher:
avail[elt] = numb - 1
if numb > 0:
matches = matches + 1
return 2.0 * matches / (len(self.a) + len(self.b))
return _calculate_ratio(matches, len(self.a) + len(self.b))
def real_quick_ratio(self):
"""Return an upper bound on ratio() very quickly.
@ -652,7 +657,7 @@ class SequenceMatcher:
la, lb = len(self.a), len(self.b)
# can't have more matches than the number of elements in the
# shorter sequence
return 2.0 * min(la, lb) / (la + lb)
return _calculate_ratio(min(la, lb), la + lb)
def get_close_matches(word, possibilities, n=3, cutoff=0.6):
"""Use SequenceMatcher to return list of the best "good enough" matches.