inspect.signature: Support classes without user-defined __init__/__new__ #20308
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 9436e35..2211b8d 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1561,6 +1561,17 @@
init = _get_user_defined_method(obj, '__init__')
if init is not None:
sig = signature(init)
+
+ if sig is None:
+ if type in obj.__mro__:
+ # 'obj' is a metaclass without user-defined __init__
+ # or __new__. Return a signature of 'type' builtin.
+ return signature(type)
+ else:
+ # We have a class (not metaclass), but no user-defined
+ # __init__ or __new__ for it
+ return signature(object)
+
elif not isinstance(obj, _NonUserDefinedCallables):
# An object with __call__
# We also check that the 'obj' is not an instance of
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index f5f18f0..a6b4c7a 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -2045,6 +2045,20 @@
('bar', 2, ..., "keyword_only")),
...))
+ # Test classes without user-defined __init__ or __new__
+ class C: pass
+ self.assertEqual(str(inspect.signature(C)), '()')
+ class D(C): pass
+ self.assertEqual(str(inspect.signature(D)), '()')
+
+ # Test meta-classes without user-defined __init__ or __new__
+ class C(type): pass
+ self.assertEqual(str(inspect.signature(C)),
+ '(object_or_name, bases, dict)')
+ class D(C): pass
+ self.assertEqual(str(inspect.signature(D)),
+ '(object_or_name, bases, dict)')
+
def test_signature_on_callable_objects(self):
class Foo:
def __call__(self, a):