Advertisements I’ve noticed that duck typing works reasonably well up to a certain point in checking whether a class is an instance of an abstract class. For example, to be an instance of collections.abc.Sized, we only need to define a __len__() method: import collections.abc class MySized: def __len__(self): return 0 assert isinstance(MySized(), collections.abc.Sized) # It… Read More The implementation of Sequence interface is not sufficient to be a Sequence

Advertisements Considering the following structure of classes: from abc import ABC, abstractmethod class ModelSettings(ABC): … class BlueModelSettings(ModelSettings): … class RedModelSettings(ModelSettings): … class Model(ABC): @abstractmethod def compute(self, settings: ModelSettings): … class BlueModel(Model): def compute(self, settings: BlueModelSettings): … class RedModel(Model): def compute(self, settings: RedModelSettings): … MyPy is complaining that the implementations of compute in BlueModel and RedModel… Read More Alternative that doesn't violate the Liskov substitution principle