案例补充：员工注册登录系统实现

while True:
    print("""
        1. 注册
        2. 登录
    """)
    
    cmd = input('请输入你的选择：').strip()
    
    # cmd的验证
    if cmd == '1':
        while True:
            # 1. 接收用户名和密码
            username = input('username>>>:')
            password = input('password>>>:')

            # 3. 判断用户是否已经注册过
            # 3.1 先取出文件中得数据
            with open('userinfo.txt', 'r', encoding='utf-8') as f1:
                # 3.2 把文件数据一行一行的读出来
                for line in f1:
                    # print(line)  # kevin|123\n
                    real_username, *_ = line.split('|')
                    # res = line.split('|')
                    if real_username == username:
                        print('该用户已经存在，请从新输入')
                        break
                else:
                    # 2. 组织用户名和密码成固定格式 kevin|123
                    data = '%s|%s\n' % (username, password)
                    # data = username + '|' + password

                    # 3. 把用户数据保存到文件中
                    with open('userinfo.txt', 'a', encoding='utf-8') as f:
                        f.write(data)

                    print('%s: 注册成功' % username)
    elif cmd =='2':
        username = input('username>>>:')
        password = input('password>>>:')

        # 2. 读取文件数据，得到用户的真实用户名和密码
        with open('userinfo.txt', 'r', encoding='utf-8') as f:
            # 一行一行的读取用户名和密码
            for line in f:
                real_username, real_pwd = line.split('|')  # kevin|123\n  ['kevin', '123\n']
                real = real_pwd.strip('\n')
                # 判断用户名和密码是否正确
                if real_username == username and real == password:
                    print('登录成功')
                    break
            else:
                print('登录失败')