超载Python类属性的一种优雅的方式

Question

考虑一个基类：

class A(object): 
    def __init__(self, x): 
     self._x = x 

    def get_x(self): 
     #... 
     return self._x 

    def set_x(self, x): 
     #... 
     self._x = x 

    x = property(get_x, set_x) 

和派生类：

class B(A): 
    def set_x(self, x): 
     #... 
     self._x = x**2 

    x = property(A.get_x, set_x) 

是否有B类重载set_x()优雅的方式，无需再宣布它和财产x？谢谢。

Answer 1

尝试这一个：

class A(object): 
    def __init__(self): 
     self._x = 0 

    def get_x(self): 
     #... 
     return self._x 

    def set_x(self, x): 
     #... 
     self._x = x 

    x = property(get_x, lambda self,x : self.set_x(x)) 

class B(A): 
    def set_x(self, x): 
     #... 
     self._x = x**2 

由lambda给出的额外间接方法将使虚拟set_x函数成为可能。

Answer 2

添加额外的间接层（即使用一个钩子）：

class A(object): 
    def __init__(self, x): 
     self._x = x 

    # Using a _get_hook is not strictly necessary for your problem... 
    def _get_hook(self): 
     return self._x 
    def get_x(self): 
     return self._get_hook() 

    # By delegating `set_x` behavior to `_set_hook`, you make it possible 
    # to override `_set_hook` behavior in subclass B. 
    def _set_hook(self, x): 
     self._x=x 
    def set_x(self, x): 
     self._set_hook(x) 

    x = property(get_x, set_x) 

class B(A): 
    def _set_hook(self, x): 
     print('got here!') 
     self._x = x**2 

b=B(5) 
b.x=10 
# got here! 
print(b.x) 
# 100 

---

对于Python的现代版本，你也可以使用@property装饰：

class A(object): 

    @property 
    def x(self): 
     return self._get_hook() 

    @x.setter 
    def x(self, x): 
     self._set_hook(x)