Python定製屬性與設置器

Question

我正在尋找python屬性內置的純python實現來了解初始化如何工作。我發現很多處理描述符接口（獲得,集合）但沒有描述setter或deleter方法。 this（大致）是如何實現的？

Answer 1

屬性是一個簡單，直接的描述符。描述符協議由三種方法組成：__get__，__set__和__delete__。每個操作的屬性只是調用用戶提供的函數。

class my_property(object): 
    def __init__(self, getter, setter, deleter): 
     self.getter = getter 
     self.setter = setter 
     self.deleter = deleter 

    def __get__(self, instance, owner): 
     return self.getter(instance) 

    def __set__(self, instance, value): 
     self.setter(instance, value) 

    def __delete__(self, instance): 
     self.deleter(instance) 

class Foo(object): 
    def __init__(self): 
     self._x = 42 

    def get_x(self): 
     print 'getter' 
     return self._x 

    def set_x(self, value): 
     print 'setter' 
     self._x = value 

    def del_x(self): 
     print 'deleter' 
     del self._x 

    x = my_property(get_x, set_x, del_x) 

obj = Foo() 
print obj.x 
obj.x = 69 
del obj.x 
print obj.x 

Answer 2

作爲評論：有一種簡單的方法可以將屬性添加到Python列表對象中。在一堂課中翹曲。

>>> class Foo(list): pass 
>>> l = Foo([1,2,3]) 
>>> l.foo = 'bar' 
>>> l 
[1, 2, 3]