test_functools.py 文件源码

def test_lru_with_exceptions(self):
        # Verify that user_function exceptions get passed through without
        # creating a hard-to-read chained exception.
        # http://bugs.python.org/issue13177
        for maxsize in (None, 100):
            @functools.lru_cache(maxsize)
            def func(i):
                return 'abc'[i]
            self.assertEqual(func(0), 'a')
            with self.assertRaises(IndexError) as cm:
                func(15)
            self.assertIsNone(cm.exception.__context__)
            # Verify that the previous exception did not result in a cached entry
            with self.assertRaises(IndexError):
                func(15)