今天学习了python写购物车的程序，受益匪浅。

1、学会了打印如何列表list。

for item in product_list:

　　print(item)

2、学会了一个取下标的函数。product_list.index(item)

3、学会了enumerate(a)

　　a=[1,2,3]

　　enumerate(a）

》》》for i in enumerate(a):print(i)

# author:zfp

product_list=[('Iphone',5800),
          ('zfp python',88),
          ('pen',2),
          ('desk',380),
          ('huawei mobiphone',2700)
          ]
shopping_cart=[]
salary=input("Input your salary:")
if salary.isdigit():
    salary=int(salary)
    while True:
        #for item in product_list:
            #print(product_list.index(item),item)
        for index,item in enumerate(product_list):
            print(index,item)
        user_choice=input("选择要买什么？>>>:")
        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:#买的起
                    shopping_cart.append(p_item)
                    salary-=p_item[1]
                    print("Added %s into shopping cart,your current salary is %s"%(p_item,salary))
                else:
                    print("你的余额不够哦，只有%s还买个卵呀" % salary)
            else:
                print("product code [%s] is not exist!"% user_choice)
        elif user_choice=='q':
            print("-------shopping  list ---------")
            for p in shopping_cart:
                print(p)
            print("Your current balance:",salary)
            exit()
        else:
            print("Invalid option")