利用yield 实现Xrange功能

 def xrange(n):
     start = 0
     while True:
         if start>n:
             return
         yield start
         start+=1
 obj = xrange(5)
 n1 = obj.__next__()
 n2 = obj.__next__()
 n3 = obj.__next__()
 n4 = obj.__next__()
 n5 = obj.__next__()
 n6 = obj.__next__()
 n7 = obj.__next__()

 print(n1,n2,n3,n4,n5,n6,n7)