python入门：最基本的用户登录用户登录，三次错误机会

 #!/usr/bin/env python
 # -*- coding:utf-8 -*-
 #用户登录，三次错误机会
 """
 导入getpass，给x赋值为1，while真，循环开始，
 user的赋值等于用户输入的内容，pwd的赋值等于用户输入的内容并且不可见
 如果用户输入user的赋值等于"admin"而且用户输入pwd的赋值等于"admin888"
 打印"login successfully!(登陆成功！)"换行 打印"welcome!:(欢迎:)user",break跳出当前循环
 否则如果x的赋值等于3，打印"Failure three times!(失败三次！)"break跳出当前循环
 否则打印"login failure!There are three more chances!(登录失败！有三次机会)"
 x的赋值每循环一次加1，当循环3次后就满足了x赋值为3，break跳出当前循环！
 """
 import getpass
 x = 1
 while True:
     user = raw_input("user:")
     pwd = getpass.getpass('password:')
     if user == "admin" and pwd == "admin888":
         print("login successfully!" + "\n" +"welcome!:" + user)
         break
     elif x == 3:
         print("Failure three times!")
         break
     else:
         print("login failure!There are three more chances!")
     x += 1