diff --git a/Lib/functools.py b/Lib/functools.py index 075418b1605a48..59fc2a8fbf6219 100644 --- a/Lib/functools.py +++ b/Lib/functools.py @@ -602,6 +602,9 @@ def decorating_function(user_function): return decorating_function def _lru_cache_wrapper(user_function, maxsize, typed, _CacheInfo): + if not callable(user_function): + raise TypeError("the first argument must be callable") + # Constants shared by all lru cache instances: sentinel = object() # unique object used to signal cache misses make_key = _make_key # build a key from the function arguments diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py index 94b469397139c7..3801a82a610891 100644 --- a/Lib/test/test_functools.py +++ b/Lib/test/test_functools.py @@ -2157,6 +2157,13 @@ def fib(n): with self.assertRaises(RecursionError): fib(support.exceeds_recursion_limit()) + def test_lru_checks_arg_is_callable(self): + with self.assertRaisesRegex( + TypeError, + "the first argument must be callable", + ): + self.module.lru_cache(1)('hello') + @py_functools.lru_cache() def py_cached_func(x, y): diff --git a/Misc/NEWS.d/next/Library/2026-01-19-12-48-59.gh-issue-144030.7OK_gB.rst b/Misc/NEWS.d/next/Library/2026-01-19-12-48-59.gh-issue-144030.7OK_gB.rst new file mode 100644 index 00000000000000..ef3c02925405b8 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-01-19-12-48-59.gh-issue-144030.7OK_gB.rst @@ -0,0 +1,3 @@ +The Python implementation of :func:`functools.lru_cache` differed from the +default C implementation in that it did not check that its argument is +callable. This discrepancy is now fixed and both raise a :exc:`TypeError`.