单例模式

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

class Myclass(Singleton):
    a=1

one=Myclass()
two=Myclass()
print(one==two)
print(one is two)
print(id(one),id(two))

#True
#True
#1268707849048 1268707849048