python propery:类似列表的对象

Question

我正在尝试创建一个具有类似列表的属性的对象.这就是我的意思.

class Unit:

    def __init__(self):
        self.val = 0

class Bundle:

    def __init__(self, N=3):
        self.units = [ Unit() for i in range(N) ]

    def getvals(self):
        return [ unit.val for unit in self.units ]

    def setvals(self, vals):
        for i, val in enumerate(vals):
            self.units[i].val = val

    vals = property(getvals, setvals)

现在,此对象的行为不符合预期.

>>> b = Bundle()
>>> b.setvals([1,2,3])
>>> print b.vals, b.getvals()
[1, 2, 3] [1, 2, 3]
>>> b.vals = [4,5,6]
>>> print b.vals, b.getvals()
[4, 5, 6] [1, 2, 3]

所以语句"b.vals = x"和"b.setvals(x)"不等同.你能告诉我为什么,以及如何让它表现得正常吗？

Answer 1

在Python 2中,property仅适用于新样式对象; 你的Bundle班级必须继承自object:

class Bundle(object):
    ...

一旦您进行了更正,该物业将按预期工作:

>>> b.vals = [4,5,6]
>>> b.vals
[4, 5, 6]
>>> b.getvals()
[4, 5, 6]
>>> [unit.val for unit in b.units]
[4, 5, 6]