在Python中将属性添加到类时执行方法

Question

我想实例化一个类，比如Fighter，有和没有属性weapon_size。但是当属性weapon_size 设置时（在实例化时或以后）我想运行一些添加另一个属性damage 的方法（并且可能进行一些其他计算）。我试图通过重载 setattr 函数来做到这一点，如下所示。

我的问题：这是正确的 [和明智的] 方法吗？

class Fighter(object):
    def __init__(self, prenom, weapon_size = None):
        self._prenom = prenom
        self._weapon_size = weapon_size
        if not weapon_size is None:
            self.AddWeapon(weapon_size)

    def __setattr__(self, name, value):
            if name == "weapon_size":
                print "Adding weapon"
                self.AddWeapon(value)
                self.__dict__['_' + name] = value
            else:
                self.__dict__[name] = value

    def AddWeapon(self, x):
        self._damage = x/2.

    @property
    def weapon_size(self):
        "Weapon size"
        return self._weapon_size
    @property
    def prenom(self):
        "First name"
        return self._prenom

U = Fighter('Greg')
U.weapon_size = 9
print U.weapon_size, U._damage
>> 9 4.5
W = Fighter('Jeff', weapon_size = 11)
print W.weapon_size, W._damage
>> 11 5.5

Answer 1

您可以为特定属性定义自定义设置器。

@weapon_size.setter
def weapon_size(self, value):
    # custom code here
    self._weapon_size = value

编辑：但实际上，归根结底，我认为您只需这样做会更清洁：

class Fighter(object):
    def __init__(self, prenom, weapon_size=None):
        ...
        self.weapon_size = weapon_size
        ...

    @property
    def damage(self):
        if self.weapon_size:
            return self.weapon_size / 2
        return None