python的单例模式就是一个类的实例只能自始自终自能创建一次。应用场景比如说数据库的连接池。

#!/usr/bin/env python
# coding=utf-8

class Foo(object):

    instance = None

    def __init__(self, name):
        self.name = name


    @classmethod
    def get_instance(cls):
        if cls.instance:
            return cls.instance
        else:
            obj = cls('hexm')
            cls.instance = obj
            return obj

obj = Foo.get_instance()
obj1 = Foo.get_instance()
print(obj.name)
print(obj1.name)
print(Foo.instance)
print(obj)