consider the example @decorator_without_args def function(): pass this is equivalent to function = decorator_without_args(function) now

consider the example @decorator_without_args def function(): pass this is equivalent to function = decorator_without_args(function) now consider the other case, where the decorator takes in some args: @dec_with_args("hello", "world") def func(): pass this is equivalent to function = decorator_with_args("hello", "world")(function) Or in other words, the expression after @ needs to evaluate to a Callable which is then called on the function you are decorating, so with @a_decorator, you call a_decorator on your function. When you use @with_args(1, 2, 3), you are calling the function "with_args" and then the result of that function is your decorator. So an example of this working is like so: debug_list = [] other_list = [] def dynamic_debug_decorator(output_list=debug_list): # dynamic debug decorator should return a decorator function # realistically, ddd is a decorator factory, not a decorator def debug_decorator(function): # so this is our real decorator def decorated_function(*args, **kwargs): # and this is the new function we return output_list.append(function) # because silly example return function(*args, **kwargs) return decorated_function return debug_decorator so now using that decorator: @dynamic_debug_decorator def function(): pass this fails, because dynamic debug decorator takes a list, but is now receiving a function. Instead we need to call it like so: @dynamic_debug_decorator def function(): pass this works, using the default values.