Equivalent of NotImplementedError for fields in Python

Question

In Python 2.x when you want to mark a method as abstract, you can define it like so:

class Base:
    def foo(self):
        raise NotImplementedError(\"Subcl         


        

Answer 1

An interesting pattern to handle this is to set attribute to None in the parent class and to access the attribute with a function that ensure it has been set in the child class.

Here is an example from django-rest-framework:

class GenericAPIView(views.APIView):

    [...]

    serializer_class = None

    [...]

    def get_serializer_class(self):
        assert self.serializer_class is not None, (
            "'%s' should either include a `serializer_class` attribute, "
            "or override the `get_serializer_class()` method."
            % self.__class__.__name__
        )

        return self.serializer_class