Python文件处理之购物车系统

一、Python文件处理之购物车系统

• 用户名和密码存放于文件中，格式为：nick,nick123
• 加载所有用户名,检查用户名是否已存在
• 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
• 允许用户根据商品编号购买商品
• 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
• 可随时退出，退出时，打印已购买商品和余额

import os

product_list = [
    ['iphone17', 998],
    ['Python教程', 9.9],
    ['su7', 2000],
    ['byd', 999],
    ['coke', 1.8],
    ['锅巴', 20]
]
shopping_cart = {}  # 存储用户购物车信息的字典
current_userinfo = []  # 存储当前登录用户的信息
# 原始字符串，避免被转义
db_file = r'D:\db.txt'  # 用户数据文件路径
while True:
    print('登录\n注册\n购物')
    choice = input('>>:').strip()
    if choice == '1':
        flag = True
        count = 0
        while flag:
            if count == 3:
                print('尝试次数过去，退出程序。。。')
                break
            uname = input('用户名：').strip()
            password = input('密码：').strip()
            with open(db_file, 'r', encoding='utf-8') as f:
                for line in f:
                    line = line.strip()
                    user_info = line.split(',')
                    uname_db = user_info[0]
                    pwd_db = user_info[1]
                    balance_db = int(user_info[2])
                    if uname == uname_db and password == pwd_db:
                        print('登录成功！')
                        current_userinfo = [uname_db, balance_db]
                        print('用户信息：', current_userinfo)
                        flag = False
                        break
                else:
                    print('检查用户名或密码错误！')
                    count += 1
    elif choice == '2':
        # 步骤1：预先加载所有用户名
        existing_users = set()
        try:
            with open(db_file, 'r', encoding='utf-8') as f:
                for line in f:
                    parts = line.strip().split(',')
                    if parts:  # 确保非空行
                        existing_users.add(parts[0])
        except FileNotFoundError:
            # 文件不存在时创建空集合
            existing_users = set()

        # 步骤2：用户名输入与验证循环
        while True:
            uname = input('请输入用户名：').strip()
            # 检查用户名是否已存在
            if uname in existing_users:
                print(f"用户名 '{uname}' 已被占用，请选择其他用户名")
            else:
                break  # 唯一用户名，退出循环

        while True:
            password1 = input('情输入密码：').strip()
            password2 = input('情确认密码：').strip()
            if password1 == password2:
                break
            else:
                print('两次输入密码不一致，请再次输入！！')
        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, password1, balance))
    elif choice == '3':
        # 登录成功，开始购物
        uname_db = current_userinfo[0]
        balance_db = current_userinfo[1]
        print(f'尊敬的用户{uname_db},您的账户余额为{balance_db}')
        flag = True
        while flag:
            for index, product in enumerate(product_list):
                print(index, product)
            choice = input('输入商品的编号购物，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_db > pprice:
                    if pname in shopping_cart:
                        shopping_cart[pname]['count'] += 1
                    else:
                        shopping_cart[pname] = {
                            'pprice': pprice,
                            'count': 1
                        }
                    balance_db -= pprice
                    current_userinfo[1] = balance_db
                    print(
                        "Added product " + pname +
                        " into shopping cart,your current balance "
                        + str(balance_db))
                else:
                    print(f'你太穷了！商品价格是{pprice},你还差{pprice - balance_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_db))
                while flag:
                    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_db):  # 字符串前缀匹配
                                    l = line.strip('\n').split(',')  # 移除行尾换行符,按逗号分割字符串
                                    l[-1] = str(balance_db)
                                    line = ','.join(l) + '\n'
                                write_f.write(line)
                        os.remove(src_file)
                        os.rename(dst_file, src_file)
                        print('购买成功，耐心等待发货。')
                    # 重置购物车,清除用户会话,退出购物循环
                    shopping_cart = {}
                    current_userinfo = []
                    flag = False
            else:
                print("输入形式非法")
    elif choice == 'q':
        break
    else:
        print('非法操作')