From: dgpb <3577712+dg-pb@users.noreply.github.com>
Date: Mon, 23 Feb 2026 01:59:40 +0000 (+0200)
Subject: gh-145131: difflib.Differ._fancy_replace performance (re-use ratio) (#145133)
X-Git-Tag: v3.15.0a7~179
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=79f6caf8f1f52788e15c97debd822e99672e5181;p=thirdparty%2FPython%2Fcpython.git

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

re-use calculated ratio
---

diff --git a/Lib/difflib.py b/Lib/difflib.py
index 7c7e233b013a..8f3cdaed9564 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -942,10 +942,12 @@ class Differ:
                 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