Python 3.5中的抽象方法的主体

问题描述

我有一个抽象类Model，其中包含一些抽象方法，我应该在方法主体中添加什么?

I have an abstract class, Model, with a few abstract methods, what should I put in the body of the methods?

1. 退货

1. A return

class Model(metaclass=ABCMeta):
    @abstractmethod
    def foo(self): return

通行证

A pass

class Model(metaclass=ABCMeta):
    @abstractmethod
    def foo(self): pass

引发描述性错误

Raising a descriptive error

class Model(metaclass=ABCMeta):
    @abstractmethod
    def foo(self):
        raise NotImplementedError("Class {class_name} doesn't implement {func_name} function"
                              .format(class_name=self.__class__.__name__, func_name=self.foo.__name__))

通常，我将实现方法3并引发错误，但是由于Python为我引发了错误，因此这似乎是多余的:

Typically I would implement method 3 and raise an error, however it looks like it would be redundant, as Python raises an error for me:

>>> bar = module.Model()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class Model with abstract methods foo

在给出的选项之间，哪种是最佳做法?还是我还有其他方法可以解决这个问题?

推荐答案

放置在abstractmethod(或abstractproperty)正文中的最佳方法是文档字符串.

The best thing to put in the body of an abstractmethod (or abstractproperty) would be a docstring.

那么您就不需要pass或return或...了，因为其中隐含了return None-并且文档字符串使此结构可以在没有SyntaxError的情况下编译":

Then you don't need pass or return or ... because a return None is implicitly included - and a docstring makes this construct "compile" without a SyntaxError:

from abc import abstractmethod, ABCMeta

class Model(metaclass=ABCMeta):
    @abstractmethod
    def foo(self):
        """This method should implement how to foo the model."""

然后，文档字符串应说明应在此处实现的内容，以便子类生成器知道/打算使用什么.

The docstring should then explain what should be implemented here so that subclassers know what is/was intended.

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