We can change the behavior of the code at run time (Dynamic modifications) is called monkey patching. # parent.py class A: def func_a(self): print ("func_a() is called") In another file where we will update the whole function as below import parent def monkey_func(self): print ("monkey_func() is called") parent.A.func_a = monkey_function obj = parent.A() obj.func_a() # o/p monkey_func() is called