购物车小程序（while循环，列表）

 1 while True:
 2     salary = input("please input your salary:")
 3     if salary.isdigit():
 4         salary=int (salary)
 5         break
 6     else:
 7         print("Invalid input! please input a number:")
 8 
 9 product_cart = [['iphone6s',5800],                 #定义商品列表
10                 ['macbook',9000],
11                 ['coffee',30],
12                 ['python book',80],
13                 ['bicycle',1500]
14                 ]
15 shopping_cart = []                                 #定义购物车
16 balance=salary
17 
18 while True:
19     for i,v in  enumerate(product_cart,1):         #enumerate参数将商品列表循环打印，并且第一行从1开始 加上序号
20         print(i,v)
21 
22     choise = input("please input your selection[typing 'q' to quit]:")
23     if choise.isdigit():                           #判断是否是数字
24         choise=int(choise)
25         if choise >=1 and choise<=len(product_cart): #判断输入的字符是否符合商品列表所在的范围
26             sales =product_cart[choise-1]            #将用户选择的商品赋值给sales
27             if balance >=sales[1]:                   #判断余额是否足够购买该商品
28                 balance -=sales[1]                   #购买完后将余额减去商品价格
29                 shopping_cart.append(sales)          #将商品加入购物车
30                 print("your balance is %s :"%balance)
31                 print()
32             else:
33                 print("your balance is %s,not enough to buy this one，please try another products!"%balance,)
34                 print()
35 
36 
37         else:
38             print("no such a selection")
39     elif choise == 'q':                            #判断是否是q选择退出
40         print("your shopping cart is:")
41         for i, v in enumerate(shopping_cart, 1):   
42             print(i, v)
43         break
44     else:
45         print("Invalid typing.please typing a number!") #非数字执行的操作

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