用Python写一段用户登录的程序代码

#!/usr/bin/env python
#coding: utf8
import getpass
db = {}
def newUser():
 username = raw_input('username: ')
 if username in db:
 #添加打印颜色
 print "\033[32;1m%s already exists![0m" % username
 else:
 #屏幕不显示密码，调用getpass.getpass()
 password = getpass.getpass()
 db[username] = password #字典k-v赋值
def oldUser():
 username = raw_input('username: ')
 password = getpass.getpass()
 if username in db:
 if db.get(username) == password:#判断输入的用户名和密码是否和字典的k-v匹配
  print '\033[32;1mlogin successful!\033[0m'
 else:
  print '\033[32;1mpassword not match username\033[0m'
 else:
 print '\033[32;1musername does not exist\033[0m'
CMDs = {'n':newUser,'o':oldUser}
def showMenu():
 prompt = """(N)ew user
(O)ld user
(Q)uit
input your choice: """
 while True:
 try:#捕获ctrl+c ctrl+d的异常
  choice = raw_input(prompt).strip().lower()[0]
 except (KeyboardInterrupt, EOFError):
  choice = 'q'
 if choice not in 'noq':
  continue
 if choice == 'q':
  break
 CMDs[choice]()#这种方法相当于shell和c里面的case，很实用
if __name__ == '__main__':
 showMenu()