我如何将 abc.abstractproperty 与类方法结合起来制作 "abstract class property"？

Question

我想创建一个 "class property"，它在抽象基础 class 中声明，然后在具体实现 class 中被覆盖，同时保持可爱的断言实现必须覆盖抽象基础 class' class 属性.

虽然我看了一下 this question 我天真的尝试重新使用已接受的答案并没有奏效：

>>> import abc
>>> class ClassProperty(abc.abstractproperty):
...     def __get__(self, cls, owner):
...             return self.fget.__get__(None, owner)()
...
>>> class Base(object):
...     __metaclass__ = abc.ABCMeta
...     @ClassProperty
...     def foo(cls):
...             raise NotImplementedError
...
>>> class Impl(Base):
...     @ClassProperty
...     def foo(cls):
...             return 5
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/2rs2ts/src/myproj/env/lib/python2.7/abc.py", line 94, in __new__
    value = getattr(cls, name, None)
  File "<stdin>", line 3, in __get__
TypeError: Error when calling the metaclass bases
    unbound method foo() must be called with Impl instance as first argument (got nothing instead)

我对我应该做的事情有点迷茫。有帮助吗？

Answer 1

除了 @classmethod 装饰器之外，您还需要使用它。

class Impl(Base):
    @ClassProperty
    @classmethod
    def foo(cls):
        return 5

In [11]: Impl.foo
Out[11]: 5

我如何将 abc.abstractproperty 与类方法结合起来制作 "abstract class property"？

How can I combine abc.abstractproperty with a classmethod to make an "abstract class property"?

python

abc