class F1:
        def __init__(self,n):
            self.N=n
            print(‘F‘)
    

    class F2:
        def __init__(self,arg1):
            self.a=arg1
            print(‘F2‘)
    

    class F3:
        def __init__(self,arg2):
            self.b=arg1
            print(‘F3‘)

    ol=F1("alex)
    o2=F2(o1)
    03=F3(02)
    """"""""输出alex""""""""
    
    o3.b==>02
    02.a=01
    
    03.b.a.N