一、文件处理实战之购物车系统

  1. 用户名和密码存放于文件中，格式为：nick|nick123

  2. 启动程序后，先登录，登录成功则让用户输入工资,然后打印商品列表，失败则重新登录，超过三次则退出程序

  3. 允许用户根据商品编号购买商品

  4. 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

  5. 可随时退出，退出时，打印已购买商品和余额

import os

product_list = [
    ['Iphone7', 5800],
    ['Coffee', 30],
    ['疙瘩汤', 10],
    ['Python Book', 99],
    ['Bike', 199],
    ['ViVo X9', 2499],
]

shopping_cart = {}
current_userinfo = []

db_file = r'db.txt'

while True:
    print('''
登陆
注册
购物
    ''')

    choice = input('>>: ').strip()

    if choice == '1':
        #1、登陆
        tag = True
        count = 0
        while tag:
            if count == 3:
                print('尝试次数过多，退出。。。')
                break
            uname = input('用户名：').strip()
            pwd = input('密码：').strip()

            with open(db_file, 'r', encoding='utf-8') as f:
                for line in f:
                    line = line.strip('\n')
                    user_info = line.split(',')

                    uname_of_db = user_info[0]
                    pwd_of_db = user_info[1]
                    balance_of_db = int(user_info[2])

                    if uname == uname_of_db and pwd == pwd_of_db:
                        print('登陆成功')

                        # 登陆成功则将用户名和余额添加到列表
                        current_userinfo = [uname_of_db, balance_of_db]
                        print('用户信息为：', current_userinfo)
                        tag = False
                        break
                else:
                    print('用户名或密码错误')
                    count += 1

    elif choice == '2':
        uname = input('请输入用户名：').strip()
        while True:
            pwd1 = input('请输入密码：').strip()
            pwd2 = input('再次确认密码：').strip()
            if pwd2 == pwd1:
                break
            else:
                print('两次输入密码不一致，请重新输入！！!')

        balance = input('请输入充值金额：').strip()

        with open(db_file, 'a', encoding='utf-8') as f:
            f.write('%s,%s,%s\n' % (uname, pwd1, balance))

    elif choice == '3':
        if len(current_userinfo) == 0:
            print('请先登陆...')
        else:
            #登陆成功后，开始购物
            uname_of_db = current_userinfo[0]
            balance_of_db = current_userinfo[1]

            print('尊敬的用户[%s] 您的余额为[%s],祝您购物愉快' % (uname_of_db, balance_of_db))

            tag = True
            while tag:
                for index, product in enumerate(product_list):
                    print(index, product)
                choice = input('输入商品编号购物，输入q退出>>: ').strip()
                if choice.isdigit():
                    choice = int(choice)
                    if choice < 0 or choice >= len(product_list): continue

                    pname = product_list[choice][0]
                    pprice = product_list[choice][1]
                    if balance_of_db > pprice:
                        if pname in shopping_cart:  # 原来已经购买过
                            shopping_cart[pname]['count'] += 1
                        else:
                            shopping_cart[pname] = {
                                'pprice': pprice,
                                'count': 1
                            }

                        balance_of_db -= pprice  # 扣钱
                        current_userinfo[1] = balance_of_db  # 更新用户余额
                        print(
                            "Added product " + pname +
                            " into shopping cart,[42;1myour current balance "
                            + str(balance_of_db))

                    else:
                        print("买不起，穷逼! 产品价格是{price},你还差{lack_price}".format(
                            price=pprice, lack_price=(pprice - balance_of_db)))
                    print(shopping_cart)
                elif choice == 'q':
                    print("""
                    ---------------------------------已购买商品列表---------------------------------
                    id          商品                   数量             单价               总价
                    """)

                    total_cost = 0
                    for i, key in enumerate(shopping_cart):
                        print('%22s%18s%18s%18s%18s' %
                              (i, key, shopping_cart[key]['count'],
                               shopping_cart[key]['pprice'],
                               shopping_cart[key]['pprice'] *
                               shopping_cart[key]['count']))
                        total_cost += shopping_cart[key][
                            'pprice'] * shopping_cart[key]['count']

                    print("""
                    您的总花费为: %s
                    您的余额为: %s
                    ---------------------------------end---------------------------------
                    """ % (total_cost, balance_of_db))

                    while tag:
                        inp = input('确认购买(yes/no?)>>: ').strip()
                        if inp not in ['Y', 'N', 'y', 'n', 'yes', 'no']:
                            continue
                        if inp in ['Y', 'y', 'yes']:
                            # 将余额写入文件

                            src_file = db_file
                            dst_file = r'%s.swap' % db_file
                            with open(src_file,'r',encoding='utf-8') as read_f,\
                                open(dst_file,'w',encoding='utf-8') as write_f:
                                for line in read_f:
                                    if line.startswith(uname_of_db):
                                        l = line.strip('\n').split(',')
                                        l[-1] = str(balance_of_db)
                                        line = ','.join(l) + '\n'

                                    write_f.write(line)
                            os.remove(src_file)
                            os.rename(dst_file, src_file)

                            print('购买成功，请耐心等待发货')

                        shopping_cart = {}
                        current_userinfo = []
                        tag = False

                else:
                    print('输入非法')
    elif choice == 'q':
        break

    else:
        print('非法操作')

登陆
注册
购物
    
>>: 2
请输入用户名：nick
请输入密码：123
再次确认密码：123
请输入充值金额：10000

登陆
注册
购物
    
>>: 1
用户名：nick
密码：123
登陆成功
用户信息为： ['nick', 10000]

登陆
注册
购物
    
>>: 3
尊敬的用户[nick] 您的余额为[10000],祝您购物愉快
0 ['Iphone7', 5800]
1 ['Coffee', 30]
2 ['疙瘩汤', 10]
3 ['Python Book', 99]
4 ['Bike', 199]
5 ['ViVo X9', 2499]
输入商品编号购物，输入q退出>>: 0
Added product Iphone7 into shopping cart,[42;1myour current balance 4200
{'Iphone7': {'pprice': 5800, 'count': 1}}
0 ['Iphone7', 5800]
1 ['Coffee', 30]
2 ['疙瘩汤', 10]
3 ['Python Book', 99]
4 ['Bike', 199]
5 ['ViVo X9', 2499]
输入商品编号购物，输入q退出>>: 1
Added product Coffee into shopping cart,[42;1myour current balance 4170
{'Iphone7': {'pprice': 5800, 'count': 1}, 'Coffee': {'pprice': 30, 'count': 1}}
0 ['Iphone7', 5800]
1 ['Coffee', 30]
2 ['疙瘩汤', 10]
3 ['Python Book', 99]
4 ['Bike', 199]
5 ['ViVo X9', 2499]
输入商品编号购物，输入q退出>>: q

                    ---------------------------------已购买商品列表---------------------------------
                    id          商品                   数量             单价               总价
                    
                     0           Iphone7                 1              5800              5800
                     1            Coffee                 1                30                30

                    您的总花费为: 5830
                    您的余额为: 4170
                    ---------------------------------end---------------------------------
                    
确认购买(yes/no?)>>: yes
购买成功，请耐心等待发货

登陆
注册
购物
    
>>: q