20201231-1 购物车程序练习实例

程序讲解：
商品列表是动态的，可能随时增加，减少，所以不能写死

Step1：打印商品列表
方式1
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]

工资只输入一次，所以放循环外面
salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for item in product_list:
            print(product_list.index(item), item)

        break

方式2
不通过下标，一个更直接的方法
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]

salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)

        break
1. 关于 enumerate
>>> a = [1,2,3]
>>> for i in enumerate(a):print(i)
...
(0, 1)
(1, 2)
(2, 3)
每一个 i 都变成了 一个元组 第一个是小标，第二个是数据本身
enumerate 做的就是 取出了 列表的下标

Step2：根据用户选择做判断
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
shopping_list = []
salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买嘛？>>>:")
        if user_choice.isdigit():
            user_choice = int(user_choice)
            if user_choice < len(product_list) and user_choice >= 0:
                # 接下来判断钱是否够用
                p_item = product_list[user_choice]
                if p_item[1] <= salary:    # 买的起
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Added %s into shopping cart, your current balance is %s" %(p_item, salary))
        elif user_choice == 'q':
            print('exit....')
        else:
            print("invalid option")
1. 如果想给结果变个颜色，红色 31，绿色 32
print("Added %s into shopping cart, your current balance is 33[31;1m%s33[0m" %(p_item, salary))
这个就是死记,后面 033[0m 一定要关闭
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
shopping_list = []
salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买嘛？>>>:")
        if user_choice.isdigit():
            user_choice = int(user_choice)
            if user_choice < len(product_list) and user_choice >= 0:
                # 接下来判断钱是否够用
                p_item = product_list[user_choice]
                if p_item[1] <= salary:    # 买的起
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Added %s into shopping cart, your current balance is 33[31;1m%s33[0m" %(p_item, salary))
        elif user_choice == 'q':
            print('exit....')
        else:
            print("invalid option")
2. 这是能买得起的情况，如果买不起呢？
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
shopping_list = []
salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买嘛？>>>:")
        if user_choice.isdigit():
            user_choice = int(user_choice)
            if user_choice < len(product_list) and user_choice >= 0:
                # 接下来判断钱是否够用
                p_item = product_list[user_choice]
                if p_item[1] <= salary:    # 买的起
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Added %s into shopping cart, your current balance is 33[31;1m%s33[0m" %(p_item, salary))
                else:
                    print("33[41;1m你的余额只剩[%s]啦，还买个毛线33[0m"%salary)
                    2-1 31 和 41 的区别
                    32 是绿色，42 就是背景是绿色
        elif user_choice == 'q':
            print('exit....')
        else:
            print("invalid option")


3. 如果现在想退出了，打印已经买的产品
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
shopping_list = []
salary = input("Input your salary: ")
if salary.isdigit():
    salary = int(salary)
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买嘛？>>>:")
        if user_choice.isdigit():
            user_choice = int(user_choice)
            if user_choice < len(product_list) and user_choice >= 0:
                # 接下来判断钱是否够用
                p_item = product_list[user_choice]
                if p_item[1] <= salary:    # 买的起
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Added %s into shopping cart, your current balance is 33[31;1m%s33[0m" %(p_item, salary))
                else:
                    print("33[41;1m你的余额只剩[%s]啦，还买个毛线33[0m"%salary)
        elif user_choice == 'q':
            print("-------shopping list--------")
            for p in shopping_list:
                print(p)
            3-1. 最后是退出，用exit()
            print("Your current balance:",salary)
            exit()
        else:
            print("invalid option")

4. 现在可以输入 6 应该如何处理？
product_list = [
    ('Iphone',5800),
    ('Mac Pro',9800),
    ('Bike',800),
    ('Watch',10600),
    ('Coffee',31),
    ('Alex Python',120),
]
shopping_list = []
salary = input("Input your salary: ")                   # 输入工资，判断是不是数字
if salary.isdigit():                                    # 如果是数字
# 如果输入的工资不是数字，就退出了，可以加 else 判断
    salary = int(salary)                                # 将其int
    while True:
        for index, item in enumerate(product_list):
            print(index, item)
        user_choice = input("选择要买嘛？>>>:")
        if user_choice.isdigit():
            user_choice = int(user_choice)

            if user_choice < len(product_list) and user_choice >= 0:
                # 接下来判断钱是否够用
                p_item = product_list[user_choice]
                if p_item[1] <= salary:    # 买的起
                    shopping_list.append(p_item)
                    salary -= p_item[1]
                    print("Added %s into shopping cart, your current balance is 33[31;1m%s33[0m" %(p_item, salary))
                else:
                    print("33[41;1m你的余额只剩[%s]啦，还买个毛线33[0m"%salary)
            # 4-1 如果输入的数字不在范围内
            else:
                print("product code [%s] is not exist!"% user_choice)

        elif user_choice == 'q':
            print("-------shopping list--------")
            for p in shopping_list:
                print(p)
            print("Your current balance:",salary)
            exit()
        else:
            print("invalid option")