From e3cf5fa9246c4b38cd5342ad6d60dd359d1e8cb6 Mon Sep 17 00:00:00 2001
From: Pieter Eendebak <pieter.eendebak@gmail.com>
Date: Tue, 5 May 2026 20:51:01 +0200
Subject: [PATCH 1/2] inspect: fast path _shadowed_dict for type

---
 Lib/inspect.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Lib/inspect.py b/Lib/inspect.py
index d3af61b26e280a..344933ce4b1b9f 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1740,6 +1740,9 @@ def _shadowed_dict(klass):
     # destroyed, and the dynamically created classes happen to be the only
     # objects that hold strong references to other objects that take up a
     # significant amount of memory.
+    # Fast path: `type` is the dominant caller; result is always _sentinel.
+    if klass is type:
+        return _sentinel
     return _shadowed_dict_from_weakref_mro_tuple(
         *[make_weakref(entry) for entry in _static_getmro(klass)]
     )

From dbd9fcf4970db7acde5368b0ac7c4adadc73ef38 Mon Sep 17 00:00:00 2001
From: Pieter Eendebak <pieter.eendebak@gmail.com>
Date: Tue, 5 May 2026 21:18:30 +0200
Subject: [PATCH 2/2] inspect: cache last metaclass in _check_class MRO loop

Consecutive MRO entries usually share their metaclass, so call
_shadowed_dict at most once per distinct metaclass.
---
 Lib/inspect.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Lib/inspect.py b/Lib/inspect.py
index 344933ce4b1b9f..b2d105cffa20ec 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1706,9 +1706,13 @@ def _check_instance(obj, attr):
 
 
 def _check_class(klass, attr):
+    last_meta = None
     for entry in _static_getmro(klass):
-        if _shadowed_dict(type(entry)) is _sentinel and attr in entry.__dict__:
-            return entry.__dict__[attr]
+        meta = type(entry)
+        if meta is last_meta or _shadowed_dict(meta) is _sentinel:
+            last_meta = meta
+            if attr in entry.__dict__:
+                return entry.__dict__[attr]
     return _sentinel