__new__ 与 __init__的区别

原文地址：http://www.cnblogs.com/ifantastic/p/3175735.html

单例模式

class Singleton(object):
    def __new__(cls, *args, **kwargs):
        if not hasattr(cls, '_instance'):
            cls._instance = super(Singleton, cls).__new__(cls, *args, **kwargs)
        return cls._instance