python 元类型编程, 单例模式SingleTon的一种实现方式

#-*- coding: UTF-8 -*-
#-------------------------------------------------------------------------------
# Name:        ģ��shell
# Purpose:     Ӧ�ó����main��ں���
#
# Author:      ankier
#
# Created:     26-10-2012
# Copyright:   (c) ankier 2012
# Licence:     <your licence>
#-------------------------------------------------------------------------------

class SingleTonMeta(type):
## @summary: 类初始化一个新的对象时，call到的方法。
def __call__(cls, *args):
if not hasattr(cls, 'instance'):
cls.instance = super(SingleTonMeta, cls).__call__(*args)
#返回单实例
return cls.instance

class Cache(object):
__metaclass__ = SingleTonMeta

def main():
cache1 = Cache()# 将call SingleTonMeta.__call__
cache2 = Cache()# 将call SingleTonMeta.__call__
print cache1 == cache2

if __name__ == '__main__':
main()

True <__main__.Cache object at 0x00BB7B30> <__main__.Cache object at 0x00BB7B30>