属性装饰器的设置方法未被调用

Question

我正在尝试使用一个属性方法来设置一个类实例的状态，下面是我的类定义：

class Result:
    def __init__(self,x=None,y=None):
        self.x = float(x)
        self.y = float(y)
        self._visible = False
        self._status = "You can't see me"

    @property
    def visible(self):
        return self._visible

    @visible.setter
    def visible(self,value):
        if value == True:
            if self.x is not None and self.y is not None:
                self._visible = True
                self._status = "You can see me!"
            else:
                self._visible = False
                raise ValueError("Can't show marker without x and y coordinates.")
        else:
            self._visible = False
            self._status = "You can't see me"

    def currentStatus(self):
        return self._status

但是从结果来看，似乎设置器方法并没有被执行，尽管内部变量的值是有改变的：

>>> res = Result(5,6)
>>> res.visible
False
>>> res.currentStatus()
"You can't see me"
>>> res.visible = True
>>> res.visible
True
>>> res.currentStatus()
"You can't see me"

我哪里做错了呢？

Answer 1

在Python 2中，你必须从object继承，这样属性才能正常工作：

class Result(object):

这样做是为了让它成为一种新式类。只要做了这个改动，你的代码就能正常运行了：

>>> res = Result(5,6)
>>> res.visible
False
>>> res.visible = True
>>> res.currentStatus()
'You can see me!'