python - 带有 setter 的自定义属性

Question

我正在寻找 property 内置函数的纯 Python 实现，以了解初始化的工作原理。我发现许多处理描述符接口(interface)(__get__、__set__)但没有描述setter 或deleter方法。这是definition吗在Python Decorator Library (大致)它的实现方式？

Answer 1

属性是一个简单、直接的描述符。描述符协议(protocol)由三个方法组成:__get__、__set__和__delete__。每个操作的属性仅调用用户提供的函数。

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