5.4 if in 语句 与 for in 语句 处理元素在列表中

对比

 1 """
 2 检查特殊元素
 3 """
 4 requested_toppings=[]
 5 if requested_toppings:
 6     if requested_topping == 'green peppers':
 7         print("Sorry,we are out of green peppers right now.")
 8     else:
 9         print(f"Adding {requested_topping}.")
10 
11 print("\nAre your sure you want a plain pizza?\n")
12 
13 requested_toppings = ['mushrooms','green peppers','extra cheese']
14 for requested_topping in requested_toppings:
15     if requested_topping == 'green peppers':
16         print("Sorry,we are out of green peppers right now.")
17     else:
18         print(f"Adding {requested_topping}.")
19 
20 print("\nFinished making your pizza!")

 

 

 

requested_toppings = ['mushrooms','green peppers','extra cheese']
if requested_topping in requested_toppings:     # 提示错误,''可以
    if requested_topping == 'green peppers':
        print("Sorry,we are out of green peppers right now.")
    else:
        print(f"Adding {requested_topping}.")

 

 总结：

for requested_topping in requested_toppings:
作用：将列表中的元素遍历完
　　  变量可以直接用，不用先定义，
if 'mushrooms' in requested_toppings: 
作用：判断元素是否在列表里面

结合起来使用：
 1 """
 2 检查特殊元素：使用多个列表
 3 """
 4 available_toppings = ['mushrooms','olives','green peppers',
 5                       'pepperoni','pineapple','extra cheese']
 6 requested_toppings = ['mushrooms','french fries','extra cheese']
 7 for requested_topping in requested_toppings:     # 提示错误,''可以
 8     if requested_topping in available_toppings:
 9         print(f"Adding {requested_topping}.")
10     else:
11         print(f"Sorry,we don't have {requested_topping}.")
12 
13 print("\nFinished making your pizza!")

 

posted @ 2022-08-01 09:36  scholar-for-ever  阅读(123)  评论(0)  编辑  收藏  举报