python通过__new__实现单例模式

1 class Singleton(object):
2     def __new__(cls, *args, **kwargs):
3         if not hasattr(cls, ‘_instance‘):
4             cls._instance = super(Singleton, cls).__new__(cls, *args, **kwargs)
5         return cls._instanc

class Singleton(object):
　　 _instance = None
    def __new__(cls, *args, **kwargs):
        if not _instance:
            cls._instance = super(Singleton, cls).__new__(cls, *args, **kwargs)
        return cls._instanc