class 属性没有进入继承 class 的实例？

Question

我已经定义了 class 属性，方法是在元 class 中定义一个带有 @property 装饰器的属性，如本 SO answer 中所提议的那样。

因为我只能访问 class 定义（将从 metaclass 继承）定义后，我让它在之后继承，这要归功于中给出的技巧上面提到的SO答案。

我希望定义的 class 属性在继承 class 及其实例中都可用。但是我没有成功地在它的实例中拥有它。

那么，让我们回顾一下我当前的代码：

class TopLevel(type):
    """ TopLevel metaclass defining class properties. """
    @property
    def depth(cls) -> int:
        return cls._depth

class OtherClass:
    """ Class that will inherit from 'TopLevel' after it has been defined.
        Dummy implementation."""
    def __init__(self, var):
        self.var = var


# Making 'Otherclass' inheriting from metaclass 'TopLevel' to have available
# as class properties 'depth'.
# As per 
OtherClass = TopLevel(OtherClass.__name__,
                      OtherClass.__bases__,
                      dict(OtherClass.__dict__))
# Set a value to '_depth'
OtherClass._depth = 3

# Check OtherClass has 'depth' class property
OtherClass.depth
Out[6]: 3

# Instanciate OtherClass: instance has no 'depth' attribute?
otherclass = OtherClass(4)
otherclass.depth
Traceback (most recent call last):

  File "/tmp/ipykernel_748533/2343605532.py", line 1, in <module>
    otherclass.depth

AttributeError: 'OtherClass' object has no attribute 'depth'

这能实现吗？

编辑

说明我对@martineau' 第一条评论的回答的代码片段：

class A:
    a=2

class B(A):
    def __init__(self,var):
        self.var = var
        
b = B(42)

b.a
Out[26]: 2

b.var
Out[27]: 42

Answer 1

解决方法如下：

class TopLevel(type):
    """ TopLevel metaclass defining class properties. """
    @property
    def depth(cls) -> int:
        return cls._depth

class OtherClass:
    """ Class that will inherit from 'TopLevel' after it has been defined.
        Dummy implementation."""
    def __init__(self, var):
        self.var = var

# explicitely add property to OtherClass.__dict__
d = dict(OtherClass.__dict__)
d.update({"depth": TopLevel.depth})

OtherClass = TopLevel(OtherClass.__name__,
                      OtherClass.__bases__,
                      d)

OtherClass._depth = 3

otherclass = OtherClass(4)
print(otherclass.depth)

class 属性没有进入继承 class 的实例？

A class property does not make it to the instance of the inheriting class?

python

inheritance

编辑

class 属性 没有进入继承 class 的实例？

A class property does not make it to the instance of the inheriting class?

python

inheritance

编辑

class 属性没有进入继承 class 的实例？