gh-138912: Speedup match class patterns with only keyword sub-patterns

Doc/library/dis.rst

@@ -1755,6 +1755,17 @@ iterations of the loop.
    .. versionadded:: 3.13
 
 
+.. opcode:: MATCH_CLASS_GET_OPT_ATTR (namei)
+
+   Replaces ``STACK[-1]`` with ``getattr(STACK[-1], co_names[namei])`` and gets
+   optional attribute from match subject ``STACK[-2]``.
+
+   Pop ``Stack[-1]``. If attribute is found, pushes it and ``True`` onto the stack.
+   Otherwise pushes ``None`` and ``False``.
+
+   .. versionadded:: 3.16
+
+
 .. opcode:: MATCH_CLASS (count)
 
    ``STACK[-1]`` is a tuple of keyword attribute names, ``STACK[-2]`` is the class

Include/internal/pycore_magic_number.h

@@ -304,6 +304,7 @@ Known values:
     Python 3.16a1 3704 (Replace DELETE_ATTR with PUSH_NULL; STORE_ATTR)
     Python 3.16a1 3705 (Add INTRINSIC_ADD_CONDITIONAL_ANNOTATION)
     Python 3.16a1 3706 (Add INTRINSIC_MATCH_CLASS_ISINSTANCE)
+    Python 3.16a1 3707 (Add MATCH_CLASS_GET_OPT_ATTR opcode)
 
     Python 3.17 will start with 3750
 
@@ -313,7 +314,7 @@ Known values:
 
 */
 
-#define PYC_MAGIC_NUMBER 3706
+#define PYC_MAGIC_NUMBER 3707
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \

Lib/test/test_peepholer.py

@@ -788,6 +788,14 @@ def test_static_swaps_match_mapping(self):
                 self.assertNotInBytecode(code, "SWAP")
 
     def test_static_swaps_match_class(self):
+        swaps = {
+            "C(a=a, b=_, c=_)",
+            "C(a=a, b=_, c=c)",
+            "C(a=a, b=b, c=_)",
+            "C(a=a, b=b, c=c)",
+            "C(a=_, b=b, c=_)",
+            "C(a=_, b=b, c=c)",
+        }
         forms = [
             "C({}, {}, {})",
             "C({}, {}, c={})",
@@ -799,7 +807,12 @@ def test_static_swaps_match_class(self):
                 pattern = form.format(a, b, c)
                 with self.subTest(pattern):
                     code = compile_pattern_with_fast_locals(pattern)
-                    self.assertNotInBytecode(code, "SWAP")
+                    if pattern in swaps:
+                        # Swaps are expected here. Class patterns with only
+                        # keyword sub-patterns are evaluated depth first.
+                        self.assertInBytecode(code, "SWAP")
+                    else:
+                        self.assertNotInBytecode(code, "SWAP")
 
     def test_static_swaps_match_sequence(self):
         swaps = {"*_, b, c", "a, *_, c", "a, b, *_"}

Misc/NEWS.d/next/Core_and_Builtins/2026-09-28-00-08-18.gh-issue-138912.pisRAJ.rst

@@ -0,0 +1,3 @@
+Add :opcode:`MATCH_CLASS_GET_OPT_ATTR` to improve the performance of
+:keyword:`match` class patterns with only keyword sub-patterns by 10% to
+30%. Patch by Marc Mueller.