Abstract Base Class Decorator Python

doit.py

import inspect

def abstractmethod(mthd):
    def default_abstract_method(*args, **kwargs):
        call_args =  inspect.getcallargs(mthd, *args, **kwargs)
        arg_spec = inspect.getargspec(mthd)
        class_name = call_args['self'].__class__.__name__
        error_str = "{}.{}({}) method must be defined"
        raise NotImplementedError(error_str.format(class_name,
                                                   mthd.func_name,
                                                   arg_spec))
    default_abstract_method.__name__ = mthd.__name__
    return default_abstract_method


class A:
    @abstractmethod
    def doit(self):
        pass


class B(A):
    pass

x = B()
x.doit()