available_toppings={"mushrooms","olives","green peppers",
"pepperoni","pineapple","extra cheese"}
requested_toppings={"mushrooms","french fries","extra cheese"}
for requested_topping in requested_toppings :
if requested_topping in available_toppings :
print("Adding "+requested_topping+".")
else :
print("Sorry,we don't have"+requested_topping)
如上,是一个for遍历列表。
三次运行结果如下:
对于同样的内容,怎会出现不同的结果?