我想声明一个带有抽象方法的基类,该方法具有类型化参数,以便实现类可以为该参数指定更具体的类型,例如:
from abc import ABC, abstractmethod
class Job(ABC):
pass
class EasyJob(Job):
pass
class HardJob(Job):
pass
class Worker(ABC):
@abstractmethod
def run(self, job: Job) -> None:
raise NotImplementedError()
class EasyWorker(Worker):
def run(self, job: EasyJob) -> None:
pass
class HardWorker(Worker):
def run(self, job: HardJob) -> None:
pass
但是,mypy 对此的提示是可以理解的:
line 14: error: Argument 1 of "run" is incompatible with supertype "Worker"; supertype defines the argument type as "Job"
line 18: error: Argument 1 of "run" is incompatible with supertype "Worker"; supertype defines the argument type as "Job"
Python 有什么方法可以促进这样的结构吗?
最佳答案
您可能想要Bounded Parametric Polymorphism 。另请参阅this section about bounded type variables 。
在Worker中,您想说您的方法run是通用的,因为它采用某种未指定类型的值T而T是Job的子类型。从 Worker 派生的类然后用 T 替换具体类型:
from abc import ABC, abstractmethod
from typing import Generic, TypeVar
class Job(ABC):
pass
class EasyJob(Job):
pass
class HardJob(Job):
pass
T = TypeVar('T', bound=Job)
class Worker(ABC, Generic[T]):
@abstractmethod
def run(self, job: T) -> None:
raise NotImplementedError()
class EasyWorker(Worker[EasyJob]):
def run(self, job: EasyJob) -> None:
pass
class HardWorker(Worker[HardJob]):
def run(self, job: HardJob) -> None:
pass
关于python - Mypy子类中更具体的参数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/59072637/