Python 对类值装饰器，实现值的获取、设置、删除单例对象

需求：tcp连接或http连接的获取，关闭，设置，通过装饰器，实现全局单例，任意可以修改连接对象并且保持单例对象
注意：代码来源于Kombu队列源码里面 kombu.utils.objects.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

class cached_property:
    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.__get = fget
        self.__set = fset
        self.__del = fdel
        self.__doc__ = doc or fget.__doc__
        self.__name__ = fget.__name__
        self.__module__ = fget.__module__

    # obj:是实例化类的对象，例如示例  : ConnectionHttp()
    # value:设置新值的连接对象,例如示例 : Connection
    def __get__(self, obj, type=None):
        # 获取值的时候调用
        if obj is None:
            return self
        try:
            return obj.__dict__[self.__name__]
        except KeyError:
            value = obj.__dict__[self.__name__] = self.__get(obj)
            return value

    def __set__(self, obj, value):
        # 给对象设置值的时候，调用
        if obj is None:
            return self
        if self.__set is not None:
            value = self.__set(obj, value)
        obj.__dict__[self.__name__] = value

    def __delete__(self, obj, _sentinel=object()):
        # 删除对象的时候调用
        if obj is None:
            return self
        value = obj.__dict__.pop(self.__name__, _sentinel)
        if self.__del is not None and value is not _sentinel:
            self.__del(obj, value)

    def setter(self, fset):
        return self.__class__(self.__get, fset, self.__del)

    def deleter(self, fdel):
        return self.__class__(self.__get, self.__set, fdel)


class Connection(object):
    """
        这个是一个连接类
    """
    pass

class ConnectionHttp(object):

    @cached_property
    def connection(self):
        return Connection()

    @connection.setter  # Prepares stored value
    def connection(self, value):
        if value is None:
            raise TypeError(‘Connection must be a connection‘)
        return value

    @connection.deleter
    def connection(self, value):
        # Additional action to do at del(self.attr)
        if value is not None:
            print(‘Connection {0!r} deleted‘.format(value))

if __name__ == ‘__main__‘:
    print(‘默认类的单例对象======================‘)
    conn = ConnectionHttp()
    print(conn.connection)
    print(conn.connection)
    print(‘修改类对象单例的连接===================‘)
    conn.connection = Connection()
    print(conn.connection)
    print(conn.connection)
    print(‘删除类对象单例的连接===================‘)
    del conn.connection
    print(conn.connection)

# 运行结果

默认类的单例对象======================
<__main__.Connection object at 0x0000024615232FC8>
<__main__.Connection object at 0x0000024615232FC8>
修改类对象单例的连接===================
<__main__.Connection object at 0x00000246152323C8>
<__main__.Connection object at 0x00000246152323C8>
删除类对象单例的连接===================
Connection <__main__.Connection object at 0x00000246152323C8> deleted
<__main__.Connection object at 0x0000024615232FC8>

Process finished with exit code 0