classmethod.instance_method.py

class classmethod_:
    """Allows using a classmethod also as an instance method"""
    def __init__(self, cls_method, inst_method=None):
        self.cls_method = cls_method
        self.inst_method = inst_method

    def __get__(self, obj, objtype=None):
        if obj is not None:
            return lambda *args: self.inst_method(obj, *args)
        if objtype is None:
            objtype = type(obj)
            
        return lambda *args: self.cls_method(objtype, *args)

    def instance_method(self, inst_method):
        return type(self)(self.cls_method, inst_method)
        
        
class MyClass:

    @ClassMethod
    def fromkeys(cls):
        print('cls', cls)

    @fromkeys.instance_method
    def fromkeys(self):
        print('self', self)