# 读取文件
file_name = "song.txt"

# 读取文件, r 只读模式, 读取文件需要指定文本文件的字符编码
f = open(file_name, "r", encoding="utf-8")
# 读取一行文本数据
line = f.readline()
print(line)

# 遍历所有行
for line in f:
    print(line)

# 获取所有行的
# 因为读指针已经移动到文件的结束， 所有 readlines会返回空列表
# readlines会把文件数据全部读取进入内存，以换行符进行分割
lines = f.readlines()
print(lines)

# 移动读指针到文件开始， 移动是以字节为单位
f.seek(0)
lines = f.readlines()
print(lines)
# 文件操作完毕，需要关闭文件
f.close()

import os


def flow_change(filename, old=None, new=None):
    """流式修改文件

    读原文件，把修改写入新文件，读完修改完则用新文件替换掉原文件
    """
    # 验证文件是否存在, old 和 new 是否有数据
    replece_count = 0
    if old and new and os.path.exists(filename):
        temporary_file = filename + "temp"
        with open(filename, "r", encoding="utf-8") as f_old, \
                open(temporary_file, "w", encoding="utf-8") as f_new:
            # 流式遍历文件，读取一行处理一行，写入一行
            for line in f_old:
                replece_count += line.count(old)
                temp_line = line.replace(old, new)
                f_new.write(temp_line)

        # 新文件替换原文件
        os.replace(temporary_file, filename)

        # 返回替换次数
        return replece_count


if __name__ == '__main__':
    # 获取命令行参数, 序列解包方式获取数据,  sys.argv[1:4]
    old, new, file_name = ['你却未看过一眼', "那一眼成永远", "song.txt"] # 模拟用户命令行输入
    # 调用函数修改
    flow_change(file_name, old, new)

class Login(object):
    """验证用户登录"""
    def __init__(self):
        self.__pwd_file = "user_pwd.txt"
        self.__pwd_data = self.get_pwd_data()
        self.__retries = {}

    def run(self):
        """模板方法模式， 组合其他方法"""
        while True:
            # 获取用户输入
            username = self.user_input("请输入用户名:")
            pwd = self.user_input("请输入密码")

            # 设置用户尝试次数
            self.__retries.setdefault(username, 0)
            # 检查用户登录状态
            enter_status = self.check_user(username, pwd)
            # 用户锁定或尝试次数达3次退出
            if enter_status:
                break

    def check_user(self, username, pwd):
        """校验用户是否登录"""
        user_info = [i for i in self.__pwd_data if username in i]
        if user_info:
            user, user_pwd, is_enter = user_info[0]
        else:
            print("密码或账号错误")
            return

        # 检查用户的密码 输错一次则尝试加一
        if pwd != user_pwd:
            self.__retries[username] += 1
            print("账号或密码错误")
            # 检查用户是否锁定或尝试次数是否小于三次
            if self.__retries[username] >= 2:
                self.lock_user(username)
                print("账号{}已经锁定，禁止登录".format(username))
            return

        # 检查账户是否锁定
        if is_enter == "0":
            print("账号{}已经锁定，禁止登录".format(username))
            return

        print("你好{}, 登录成功".format(username))
        return True

    def lock_user(self, username):
        """锁定用户"""
        result = []
        for item in self.__pwd_data:
            user, user_pwd, is_enter = item
            if username == user:
                result.append("{} {} {}\n".format(username, user_pwd, "0"))
            else:
                result.append(" ".join(item) + "\n")
        self.__pwd_data = result
        # 写入修改
        self.write_change()

    def write_change(self):
        """写入修改, 只有账号锁定时写入修改"""
        temp_file = self.__pwd_file + "tmp"
        with open(temp_file, "w", encoding="utf-8") as f:
            f.writelines(self.__pwd_data)

        # 替换文件
        os.replace(temp_file, self.__pwd_file)

    def user_input(self, prompt):
        """获取用户输入"""
        while True:
            data = input(prompt).strip()
            if data:
                return data

    def get_pwd_data(self):
        """获取用户存储的信息"""
        with open(self.__pwd_file, "r", encoding="utf-8") as f:
            pwd_data = [i.split() for i in f.readlines()]
        return pwd_data
if __name__ == '__main__':
    login = Login()
    login.run()