python 用户登录程序

需求：
让用户输入用户名密码
认证成功后显示欢迎信息
输错三次后退出程序
可以支持多个用户登录 
用户3次认证失败后，退出程序，再次启动程序尝试登录时，还是锁定状态

# -*- coding:utf-8 -*-
# author: Skyell

flag = True
account_list = {'xiaopang':'123','haohao':'234'}   #账号密码
username = input('Please input your username:')
lock_name = open('lockname_list.txt','r')
for i in lock_name:
    lockname = i.strip()
    if lockname == username:
        print('your account has been locked!')
        break
    else:
        continue
lock_name.close()

if username != lock_name:
    password_wrong = 0
    while flag:
        password = input('Please input your password:')
        acc_name = [keys for keys in account_list]  #利用列表生成式将账号信息存入列表中
        if username in acc_name:
            if account_list[username] == password:  #判断账号、密码是否正确
                print('welcome back!')
                flag = False
                break
            else:
                print('Please try again!')
                password_wrong +=1
                if password_wrong==3:           #密码错误3次，锁定用户
                    print('your account has been locked')
                    lock_name = open('lockname_list.txt', 'a+')
                    lock_name.write('\n')
                    lock_name.write(username)          #将被锁定的账号写入锁定文件中
                    lock_name.close()
        else:
            print('Account is not found')
            flag = False
            break

基本实现需求，继续继续！