User-defined method objects may be created when getting an attribute of a class (perhaps via an instance of that class), if that attribute is a user-defined function object, an unbound user-defined method object, or a class method object.
class A(object): # func: A user-defined function object # # Note that func is a function object when it's defined, # and an unbound method object when it's retrieved. def func(self): pass # classMethod: A class method @classmethod def classMethod(self): pass class B(object): # unboundMeth: A unbound user-defined method object # # Parent.func is an unbound user-defined method object here, # because it's retrieved. unboundMeth = A.func a = A() b = B() print A.func # output: <unbound method A.func> print a.func # output: <bound method A.func of <__main__.A object at 0x10e9ab910>> print B.unboundMeth # output: <unbound method A.func> print b.unboundMeth # output: <unbound method A.func> print A.classMethod # output: <bound method type.classMethod of <class '__main__.A'>> print a.classMethod # output: <bound method type.classMethod of <class '__main__.A'>>
When the attribute is a user-defined method object, a new method object is only created if the class from which it is being retrieved is the same as, or a derived class of, the class stored in the original method object; otherwise, the original method object is used as it is.
# Parent: The class stored in the original method object class Parent(object): # func: The underlying function of original method object def func(self): pass func2 = func # Child: A derived class of Parent class Child(Parent): func = Parent.func # AnotherClass: A different class, neither subclasses nor subclassed class AnotherClass(object): func = Parent.func print Parent.func is Parent.func # False, new object created print Parent.func2 is Parent.func2 # False, new object created print Child.func is Child.func # False, new object created print AnotherClass.func is AnotherClass.func # True, original object used