https://github.com/python/cpython/commit/21a36aa79ca0b2af49995fa1b9216b01ef98f195
commit: 21a36aa79ca0b2af49995fa1b9216b01ef98f195
branch: main
author: Vasiliy Kiryanov <[email protected]>
committer: methane <[email protected]>
date: 2026-10-16T13:16:11+09:00
summary:
gh-83731: Test that isinstance() ignores tuple subclass methods (#158000)
Add a regression test to make sure isinstance() reads the items of a
tuple subclass directly, without calling its __iter__(), __getitem__()
or __len__().
files:
M Lib/test/test_isinstance.py
diff --git a/Lib/test/test_isinstance.py b/Lib/test/test_isinstance.py
index 16d879a3831bc6..a3f4659d871919 100644
--- a/Lib/test/test_isinstance.py
+++ b/Lib/test/test_isinstance.py
@@ -263,6 +263,20 @@ def test_subclass_tuple(self):
self.assertEqual(True, issubclass(int, (int, (float, int))))
self.assertEqual(True, issubclass(str, (str, (Child, str))))
+ def test_tuple_subclass_methods_not_called(self):
+ # gh-83731: make sure isinstance() reads the items of a tuple
+ # subclass directly, without calling its __iter__(),
+ # __getitem__() or __len__().
+ class T(tuple):
+ def __iter__(self):
+ raise AssertionError('__iter__ called')
+ def __getitem__(self, index):
+ raise AssertionError('__getitem__ called')
+ def __len__(self):
+ raise AssertionError('__len__ called')
+
+ self.assertTrue(isinstance(1, T((int,))))
+
@support.skip_if_huge_c_stack()
@support.skip_wasi_stack_overflow()
@support.skip_emscripten_stack_overflow()
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