Python的for循環本質上就是通過不斷調用next()函數實現的，例如：

 1 #_*_coding:utf-8_*_
 2 #__author__ = "csy"
 3 d = ["咖啡漿果風味拿鐵","抹茶星冰樂","可可碎片星冰樂","焦糖瑪奇朵","經典巧克力","咖啡密斯朵","熱牛奶","東方美人","冰摩卡","卡布奇諾","美式咖啡","雙果果汁"]
 4 a = iter([0,1,2,3,4,5,6,8,9,10,11])
 5 while True:
 6     try:
 7         x = next(a)
 8         print(d[x])
 9
 
     except StopIteration:
10         break

輸出：

咖啡漿果風味拿鐵
抹茶星冰樂
可可碎片星冰樂
焦糖瑪奇朵
經典巧克力
咖啡密斯朵
熱牛奶
冰摩卡
卡布奇諾
美式咖啡
雙果果汁

相當於：

1 #_*_coding:utf-8_*_
2 #__author__ = "csy"
3 d = ["咖啡漿果風味拿鐵","抹茶星冰樂","可可碎片星冰樂","焦糖瑪奇朵","經典巧克力","咖啡密斯朵","熱牛奶","東方美人","冰摩卡","卡布奇諾","美式咖啡","雙果果汁"]
4 for x in range(0,12):
5     print(d[x])

Python叠代器（2） —— 實現for循環