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

Here is a simple example how to set required properties/methods for sublasses in Python 3.

class Base:
    requires = ('foo', 'bar')

    def __init_subclass__(cls, **kwargs):
        for requirement in cls.requires:
            if not hasattr(cls, requirement):
                raise NotImplementedError(
                        f'"{cls.__name__}" must have "{requirement}".')
        super().__init_subclass__(**kwargs)