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gh-145131: difflib.Differ._fancy_replace performance (re-use ratio) #145133

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Merged
tim-one merged 1 commit into from
Feb 23, 2026
Merged

gh-145131: difflib.Differ._fancy_replace performance (re-use ratio) #145133

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10 changes: 6 additions & 4 deletions Lib/difflib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -942,10 +942,12 @@ def _fancy_replace(self, a, alo, ahi, b, blo, bhi):
cruncher.set_seq1(a[i])
# Ordering by cheapest to most expensive ratio is very
# valuable, most often getting out early.
if (crqr() > best_ratio
and cqr() > best_ratio
and cr() > best_ratio):
best_i, best_j, best_ratio = i, j, cr()
if crqr() <= best_ratio or cqr() <= best_ratio:
continue

ratio = cr()
if ratio > best_ratio:
best_i, best_j, best_ratio = i, j, ratio

if best_i is None:
# found nothing to synch on yet - move to next j
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