#!/usr/bin env python
# -*- coding:utf-8 -*-
def login(user, pwd):
    """
    用于用户名密码的验证
    :param user: 用户名
    :param pwd: 密码
    :return: True,用户验证成功，Flase，用户验证失败
    """
    with open("db.log", "r", encoding="utf-8") as f:
        for line in f:
            line = line.strip()  # 去掉两端的换行符和空字符换
            ‘‘‘
            默认strip武参数：去掉空格和换行符
            有参数：移除两侧指定的值
            ‘‘‘
            line_list = line.split("$")
            if user == line_list[0] and pwd == line_list[2]:
                return True
        return False


def register(username, password):
    ‘‘‘
    注册用户
    :param username:用户名
    :param password:密码
    :return:注册成功True
    ‘‘‘
    with open("db.log", "a", encoding="utf-8") as f:
        temp = "\n" + username + "$" + password
        f.write(temp)
    return True


def user_exist(username):
    """
    判断用户是否存在
    :param username:
    :return:
    """
    with open("db.log", "r", encoding="utf-8") as f:
        for line in f:
            line = line.strip()
            line_list = line.split("$")
            if line_list[0] == username:
                return True
    return False


def main():
    print("欢迎登录XXX系统")
    inp = input("1:登录；2:注册")
    if inp == "1":
        user = input("请输入用户：")

        pwd = input("请输入密码:")
        is_login = login(user, pwd)
        if is_login:
            print("登录成功")
        else:
            print("登录失败")
    elif inp == "2":
        user = input("请输入用户：")
        pwd = input("请输入密码：")
        is_exist = user_exist(user)
        if is_exist:
            print("用户已经存在，无法注册")
        else:
            result = register(user, pwd)
            if result:
                print("注册成功")
            else:
                print("注册失败")


main()