Python 单例模式：
class Singleton(object): def __new__(cls, *args, **kw): if not hasattr(cls, ‘_instance‘): orig = super(Singleton, cls) cls._instance = orig.__new__(cls, *args, **kw) return cls._instance
Python单例实现
原文：http://www.cnblogs.com/hangshi/p/4191108.html
