python · miss-islington · May 10, 2025
diff --git a/Lib/inspect.py b/Lib/inspect.py
@@ -2074,13 +2074,11 @@ def _signature_is_functionlike(obj):
    code = getattr(obj, '__code__', None)
    defaults = getattr(obj, '__defaults__', _void) # Important to use _void ...
    kwdefaults = getattr(obj, '__kwdefaults__', _void) # ... and not None here
-    annotations = getattr(obj, '__annotations__', None)

    return (isinstance(code, types.CodeType) and
            isinstance(name, str) and
            (defaults is None or isinstance(defaults, tuple)) and
-            (kwdefaults is None or isinstance(kwdefaults, dict)) and
-            (isinstance(annotations, (dict)) or annotations is None) )
+            (kwdefaults is None or isinstance(kwdefaults, dict)))


 def _signature_strip_non_python_syntax(signature):

diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
@@ -4997,6 +4997,37 @@ def test_signature_annotation_format(self):
                with self.assertRaisesRegex(NameError, "undefined"):
                    signature_func(ida.f)

+    def test_signature_deferred_annotations(self):
+        def f(x: undef):
+            pass
+
+        class C:
+            x: undef
+
+            def __init__(self, x: undef):
+                self.x = x
+
+        sig = inspect.signature(f, annotation_format=Format.FORWARDREF)
+        self.assertEqual(list(sig.parameters), ['x'])
+        sig = inspect.signature(C, annotation_format=Format.FORWARDREF)
+        self.assertEqual(list(sig.parameters), ['x'])
+
+        class CallableWrapper:
+            def __init__(self, func):
+                self.func = func
+                self.__annotate__ = func.__annotate__
+
+            def __call__(self, *args, **kwargs):
+                return self.func(*args, **kwargs)
+
+            @property
+            def __annotations__(self):
+                return self.__annotate__(Format.VALUE)
+
+        cw = CallableWrapper(f)
+        sig = inspect.signature(cw, annotation_format=Format.FORWARDREF)
+        self.assertEqual(list(sig.parameters), ['args', 'kwargs'])
+
    def test_signature_none_annotation(self):
        class funclike:
            # Has to be callable, and have correct

diff --git a/Misc/NEWS.d/next/Library/2025-05-04-17-04-55.gh-issue-132493.huirKi.rst b/Misc/NEWS.d/next/Library/2025-05-04-17-04-55.gh-issue-132493.huirKi.rst
@@ -0,0 +1,2 @@
+Avoid accessing ``__annotations__`` unnecessarily in
+:func:`inspect.signature`.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Avoid accessing ``__annotations__`` unnecessarily in
		:func:`inspect.signature`.