python 基础 day02—training_购物车程序练习

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程序：购物车程序

需求:

1. 启动程序后，让用户输入预算，然后打印商品列表
2. 允许用户根据商品编号购买商品
3. 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 
4. 可随时退出，退出时，打印已购买商品和余额

代码：

#cherry_cui

mall_list = [
    ('Bicycle',800),
    ('computer',4800),
    ('pizza',50),
    ('skirt',200),
    ('shoes',1200),
    ('iphone6',3200),
    ('watch',2700)
]
shopping_cart =[]
budget = input("Input your budget:")                                 #输入购物预算
if budget.isdigit():                                                   #判断budget 是否只由数字组成。
    budget = int(budget)                                               #转换成int类型

    while True:
        for num,item in enumerate(mall_list):                          # enumerate()获取mall_list的下标
            print(num,item)

        choice = input("which goods you want(enter the number):")  #输入需要购买的商品编号
        if choice.isdigit():                                           #判断choice 是否只由数字组成。
            choice = int(choice)                                       #转换成int类型

            if choice < len(mall_list) and choice >= 0:               #len() 方法返回mall_list列表元素个数
                u_item = mall_list[choice]
                if u_item[1]<=budget:
                    budget-=u_item[1]
                    shopping_cart.append(u_item)                       #把已购买的商品加入购物车shopping_cart
                    print("%s had added to your shopping list,your current balance is %s !" %(u_item[0],budget))

                else:
                    print("Your current balance is %s ,not enough to buy %s ,choose again!" %(budget,u_item[0]))

            else:
                print("Product code %s is not exist,choose again" %choice)


        elif choice == 'q':
            print("-----shopping_cart-----")
            for c in shopping_cart:
                print(c)

            print("Your current balance is %s" %budget)
            exit()


        else:
            print("Input error!")
            exit()


else:
    print("Input error!")

结果：

正常流程：

Input your budget:10000
('Bicycle', 800)
('computer', 4800)
('pizza', 50)
('skirt', 200)
('shoes', 1200)
('iphone6', 3200)
('watch', 2700)

which goods you want(enter the number):1
computer had added to your shopping list,your current balance is 5200 !
('Bicycle', 800)
('computer', 4800)
('pizza', 50)
('skirt', 200)
('shoes', 1200)
('iphone6', 3200)
('watch', 2700)

which goods you want(enter the number):5
iphone6 had added to your shopping list,your current balance is 2000 !
('Bicycle', 800)
('computer', 4800)
('pizza', 50)
('skirt', 200)
('shoes', 1200)
('iphone6', 3200)
('watch', 2700)

which goods you want(enter the number):6
Your current balance is 2000 ,not enough to buy watch ,choose again!   #余额不足
('Bicycle', 800)
('computer', 4800)
('pizza', 50)
('skirt', 200)
('shoes', 1200)
('iphone6', 3200)
('watch', 2700)

which goods you want(enter the number):2
pizza had added to your shopping list,your current balance is 1950 !
('Bicycle', 800)
('computer', 4800)
('pizza', 50)
('skirt', 200)
('shoes', 1200)
('iphone6', 3200)
('watch', 2700)

which goods you want(enter the number):q              #退出程序
-----shopping_cart-----
('computer', 4800)
('iphone6', 3200)
('pizza', 50)
Your current balance is 1950

Process finished with exit code 0

  

异常一：输入的预算不为数字

异常二：输入的商品编号大于存在的商品号 / 输入的商品编号不为数字

Input your budget:1000
0 ('Bicycle', 800)
1 ('computer', 4800)
2 ('pizza', 50)
3 ('skirt', 200)
4 ('shoes', 1200)
5 ('iphone6', 3200)
6 ('watch', 2700)

which goods you want(enter the number):9
Product code 9 is not exist,choose again
0 ('Bicycle', 800)
1 ('computer', 4800)
2 ('pizza', 50)
3 ('skirt', 200)
4 ('shoes', 1200)
5 ('iphone6', 3200)
6 ('watch', 2700)

which goods you want(enter the number):dsa
Input error!

新学习的函数：

1. isdigit()     方法检测字符串是否只由数字组成

2. enumerate()     函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据和数据下标

3. len()  方法返回对象（字符、列表、元组等）长度或项目个数。

其中，获取商品下标有两种方法

1.用enumerate()函数

2.list名称.index(数值) 就能拿到对应数值的索引(下标)

for item in mall_list:
    print(mall_list.index(item), item)