class A():
    def __init__(self):
        self.heade=None
        self.next=None
        self.data=None

    def index(self,index):
        pass

a=A()
a.data='ming'

a1=A()
a1.data='ming1'
a.next=a1

head=A()
head.heade=a

head.a.data
head.a.a1.data