TL;DR Descriptor是Python实现streagy模式的一种变形，它将属性的访问／修改／删除委托给了Descriptor。

Descriptor

示例代码如下：

    class Descriptor(object):
        class_var = "cls"

        def __init__(self, *args, **kwargs):
            # Here the `super` is differ from python2: super(Descriptor, self)
            super().__init__(*args, **kwargs)

        def __get__(self, instance, owner):
            print("==")
            print(instance, owner)
            return None

        def __set__(self, instance, value):
            print(instance, value)

        def __delete__(self, instance):
            print(instance)

    class Host(object):
        desc = Descriptor()
        norm = 1

host = Host()
host.desc
host.norm

==
<__main__.Host object at 0x7ff7dbff5d68> <class '__main__.Host'>

1

host.desc = 2
host.norm = 2

<__main__.Host object at 0x7ff7dbff5d68> 2

desc = Descriptor()
    desc.__get__(None, None)

==
None None

Descriptor#

Descriptor