salary = input('please input your monthly salary: ')goods_list = [    ('iphone', 5000),    ('mac pro', 12000),    ('TV', 4500),    ('pencel', 25)]shopping_list = []if salary.isdigit():    salary = int(salary)    while True:        for index, item in enumerate(goods_list):            print('商品编号：%d, 商品名称：%s, 商品价格：%d' % (index, item[0], item[1]))        choice = input('请选择你要的商品：>>')        if choice.isdigit():            choice = int(choice)            if choice < len(goods_list) and choice >= 0:                choice_good = goods_list[choice]                if choice_good[1] <= salary:                    shopping_list.append(goods_list[choice])                    salary = salary - choice_good[1]                    print('你还有余额: %d' % salary)                else:                    print('你的余额仅有：%d啦，不够购买此商品'%salary)            else:                print('没有%d的商品编码' % choice)        elif choice == 'q':            print('-----------SHOPPING LIST----------')            for i in shopping_list:                print(i)            print('你还有余额: %d' % salary)            exit()        else:            print("请输入商品编号")else:    print('请输入工资金额')