cls只能调用一次实例 第二次None

class Zarten():
    _singleton = None
    def __new__(cls, *args, **kwargs):
        print('__new__')
        if  not cls._singleton:
            cls._singleton = object.__new__(cls)
            return cls._singleton
    def __init__(self,name,age):
        print('__init__')
        self.name = name
        self.age = age
    def __repr__(self):
        return 'YOU name %s Age is %s'%(self.name,self.age)


z = Zarten('z',35)
z1= Zarten('z1',49)
print(z)
print(z1)

__new__
__init__
__new__
YOU name z Age is 35
None