元组--购物车实战

不可变的列表，作用：存不可变的信息

实例：

启动程序后，让用户输入工资，然后打印商品列表
允许用户根据商品编号购买商品
用户选择商品后，检测余额是否够，够就直接扣款，不够就提醒
可随时退出，退出时，打印已购买商品和余额

product_list = [('Iphone', 6800), ('Watch', 10060), ('coffce', 31), ('bike', 800)]
shopping_list = []
salary = input("please input salary>>")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买的商品》》")
        if user_choice.isdigit():
            user_choice = int(user_choice)
            if user_choice < len(product_list) and user_choice >= 0:
                p_item = product_list[user_choice]
                if p_item[1] <= salary:
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Add %s into shopping_cart,your currently balance is 33[31;1m %s 33[0m" % (p_item, salary))
                else:
                    print("33[41;1m你的余额只剩[%s]啦33[0m,余额不足" % salary)
            else:
                print("product_code %s is not exist" % salary)
        elif user_choice == 'q':
            print("-------shopping_list---------------")
            for p in shopping_list:
                print(p)
            print("your currently balance is %s" % salary)
            exit()
        else:
            print("Invalid choice")
else:
    print("salary %s is not a number" % salary)