gh-142939: difflib.get_close_matches performance (#142940)

diff --git a/Lib/difflib.py b/Lib/difflib.py
index 4a0600e4ebb01b2008193b84f876368abc1948fb..7c7e233b013a7648860ab1b1f78bb7b097d899f4 100644 (file)
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -638,15 +638,15 @@ class SequenceMatcher:
         # avail[x] is the number of times x appears in 'b' less the
         # number of times we've seen it in 'a' so far ... kinda
         avail = {}
-        availhas, matches = avail.__contains__, 0
+        matches = 0
         for elt in self.a:
-            if availhas(elt):
+            if elt in avail:
                 numb = avail[elt]
             else:
                 numb = fullbcount.get(elt, 0)
             avail[elt] = numb - 1
             if numb > 0:
-                matches = matches + 1
+                matches += 1
         return _calculate_ratio(matches, len(self.a) + len(self.b))
 
     def real_quick_ratio(self):
@@ -702,10 +702,12 @@ def get_close_matches(word, possibilities, n=3, cutoff=0.6):
     s.set_seq2(word)
     for x in possibilities:
         s.set_seq1(x)
-        if s.real_quick_ratio() >= cutoff and \
-           s.quick_ratio() >= cutoff and \
-           s.ratio() >= cutoff:
-            result.append((s.ratio(), x))
+        if s.real_quick_ratio() < cutoff or s.quick_ratio() < cutoff:
+            continue
+
+        ratio = s.ratio()
+        if ratio >= cutoff:
+            result.append((ratio, x))
 
     # Move the best scorers to head of list
     result = _nlargest(n, result)

diff --git a/Misc/NEWS.d/next/Library/2025-12-29-21-12-12.gh-issue-142939.OyQQr5.rst b/Misc/NEWS.d/next/Library/2025-12-29-21-12-12.gh-issue-142939.OyQQr5.rst
new file mode 100644 (file)
index 0000000..65523f0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-29-21-12-12.gh-issue-142939.OyQQr5.rst
@@ -0,0 +1 @@
+Performance optimisations for :func:`difflib.get_close_matches`