购物车小程序（while循环，列表）

while True:
    salary = input("please input your salary:")
    if salary.isdigit():
        salary=int (salary)
        break
    else:
        print("Invalid input! please input a number:")

product_cart = [['iphone6s',5800],                 #定义商品列表
                ['macbook',9000],
                ['coffee',30],
                ['python book',80],
                ['bicycle',1500]
                ]
shopping_cart = []                                 #定义购物车
balance=salary

while True:
    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
        print(i,v)

    choise = input("please input your selection[typing 'q' to quit]:")
    if choise.isdigit():                           #判断是否是数字
        choise=int(choise)
        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
            sales =product_cart[choise-1]            #将用户选择的商品赋值给sales
            if balance >=sales[1]:                   #判断余额是否足够购买该商品
                balance -=sales[1]                   #购买完后将余额减去商品价格
                shopping_cart.append(sales)          #将商品加入购物车
                print("your balance is %s :"%balance)
                print()
            else:
                print("your balance is %s,not enough to buy this one，please try another products!"%balance,)
                print()


        else:
            print("no such a selection")
    elif choise == 'q':                            #判断是否是q选择退出
        print("your shopping cart is:")
        for i, v in enumerate(shopping_cart, 1):   
            print(i, v)
        break
    else:
        print("Invalid typing.please typing a number!") #非数字执行的操作