#__author__:Administrator} #data: 2017/11/2 product_list = [     ('Mac',9000),     ('kindel',800),     ('tesla',900000),     ('python_book',105),     ('bike',2000), ] saving = input('please input a money:') shopping_car = [] if saving.isdigit():     saving = int(saving) #方法一 # for i in product_list: #     print(product_list.index(i),i) #方法二     while True:         for i ,v in enumerate(product_list,1):             print(i,v)         choice = input('请选择商品编号[退出:q]:')         if choice.isdigit():             choice = int(choice)             if choice>0 and choice<=len(product_list):                 p_item = product_list[choice-1]                 if p_item[1]