method_not_imlemented_mixin.py

class GetAttrNotImplementedMixin:
    methods_to_be_implemented = {'foo', 'bar'}  # add more method names

    def __getattr__(self, name):
        def _method_not_implemented(*args, **kwargs):
            raise NotImplementedError("Method %s is not implemented in class %s" % (name, self.__class__.__name__))

        if name in self.methods_to_be_implemented:
            return _method_not_implemented

        raise AttributeError(self.__class__, name)


class Foo(GetAttrNotImplementedMixin):
    def __init__(self):
        self.the_answer = 42

    # Foo.bar is not implemented
    def foo(a):
        print('Foo.foo()')

class Bar(GetAttrNotImplementedMixin):
    # Bar.foo is not implemented
    def bar(a):
        print('Bar.bar()')


Foo().foo() # OK
Bar().bar() # OK

print(Foo().the_answer)

Foo().bar() #  Error

# print(Bar().the_answer) # Error

test_output.md

python$ python method_not_imlemented_mixin.py 
Foo.foo()
Bar.bar()

42

Traceback (most recent call last):
  File "method_not_imlemented_mixin.py", line 33, in <module>
    Foo().bar() #  Error
  File "method_not_imlemented_mixin.py", line 6, in _method_not_implemented
    raise NotImplementedError("Method %s is not implemented in class %s" % (name, self.__class__.__name__))
NotImplementedError: Method bar is not implemented in class Foo