python从入门到精通（DAY 3）
要求：编写登陆接口
输入用户名密码
认证成功后显示欢迎信息
输错三次后锁定
针对此实例写了有二种类型的脚本，略有不同，具体如下：
帐号文件account.txt内容如下：
sam 123
david 12
kevin 123
lin 12
tailen 123
jack 12
锁文件account_lock.txt默认为空
一、只针对帐号文件里的用户进行判断并锁定，针对用户和密码各有三次错误重试机会。
1、流程图如下：
代码如下：
#!/usr/bin/python27
#_*_ coding:utf-8 _*_
import sys,os,getpass
os.system('clear')
i = 0
while i < 3: #只要用户登录异常不超过3次就不断循环
name = raw_input("请输入用户名：")
lock_file = open('account_lock.txt','r+') #当用户输入用户名后，打开LOCK 文件 以检查是否此用户已经LOCK了
lock_list = lock_file.readlines()
for lock_line in lock_list: #循环LOCK文件
lock_line = lock_line.strip('\n') #去掉换行符
if name == lock_line: #如果LOCK了就直接退出
sys.exit('用户 %s 已经被锁定，退出' % name)
user_file = open('account.txt','r') #打开帐号文件
user_list = user_file.readlines()
for user_line in user_list: #对帐号文件进行遍历
(user,password) = user_line.strip('\n').split() #分别获取帐号和密码信息
if name == user: #如用户名正常匹配
j = 0
while j < 3: #只要用户密码异常不超过3次就不断循环
passwd = getpass.getpass('请输入密码：') #输入隐藏密码
if passwd == password: #密码正确，提示欢迎登录
print('欢迎登录管理平台，用户%s' % name)
sys.exit(0) #正常退出
else:
print('用户 %s 密码错误，请重新输入，还有 %d 次机会' % (name,2 - j))
j += 1 #密码输入错误后，循环值增加1
else:
lock_file.write(name + '\n') #密码输入三次错误后，将该用户追加到LOCK文件
sys.exit('用户 %s 达到最大登录次数，将被锁定并退出' % name)
else:
pass #当用户没匹配时，跳过并继续循环
else:
print('用户 %s 不存在，请重新输入，还有 %d 次机会' % (name,2 - i))
i += 1 #当用户输入错误时，循环值增加1
else:
sys.exit('用户 %s 不存在，退出' % name) #用户输入三次错误后，异常退出
lock_file.close() #关闭LOCK文件
user_file.close() #关闭帐号文件
二、针对帐号文件里的不存在的用户也可以进行判断并锁定，针对用户和密码共有三次错误重试机会
代码如下：
#_*_ coding:utf-8 _*_
import sys,os,getpass
os.system('clear')
retry_limit = 3
retry_count = 0
account_file = 'account.txt'
lock_file = 'account_lock.txt'
while retry_count < retry_limit: #只要重试不超过3次就不断循环
username = raw_input('\033[31;43mUsername:\033[0m')
username = username.strip()
lock_check = open(lock_file) #当用户输入用户名后，打开LOCK 文件 以检查是否此用户已经LOCK了
for line in lock_check.readlines(): #循环LOCK文件
if username == line.strip('\n'): #去掉换行符
sys.exit('\033[35mUser %s is locked!!!\033[0m' % username) #如果LOCK了就直接退出
password = raw_input('\033[32;41mPassword:\033[0m') #输入密码
f = open(account_file,'r') #打开帐号文件
match_flag = False # 默认为Flase,如果用户match 上了，就设置为 True
for line in f.readlines():
user,passwd = line.strip('\n').split() #去掉每行多余的\n并把这一行按空格分成两列，分别赋值为user,passwd两个变量
if username == user and password == passwd: #判断用户名和密码是否都相等
print('hello, %s !!' % username)
match_flag = True #相等就把循环外的match_flag变量改为了True
break #然后就不用继续循环了，直接 跳出，因为已经match上了
f.close()
if match_flag == False: #如果match_flag还为False,代表上面的循环中跟本就没有match上用户名和密码，所以需要继续循环
print('sorry,%s is unmatched' % username)
retry_count += 1 #计数器加1
else:
print('wlecome login my learning system!')
break #用户成功登录，退出脚本
else:
print("you account %s is locked!!!" % username)
g = open(lock_file,'a')
g.write(username) #被锁用户追加到用户锁文件
g.write('\n')
g.close()
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