#! /usr/bin/env python
#coding=utf-8
db = {}

def newuser():
    prompt = 'login desired: '
    while True:
        name = raw_input(prompt)
        if db.has_key(name):
            prompt = 'name taken, try another: '
            continue
        else:
            break
    pwd = raw_input('passwd: ')
    db[name] = pwd
   
def olduser():
    name = raw_input('login: ')
    pwd = raw_input('passwd: ')
    passwd = db.get(name)
    if passwd == pwd:
        print 'welcome back', name
    else:
        print 'login incorrect!'
       
def showmenu():
    promt = """
(N)ew User Login
(E)xisting User Login
(Q)uit
Enter choice: """
    done = False
    while not done:
        chosen = False
        while not chosen:
            try:
                choice = raw_input(promt).strip()[0].lower()
            except(EOFError, KeyboardInterrupt):
                choice = 'q'
            print '\nYou picked: [%s]' % choice
            if choice not in 'neq':
                print 'invalid option, try again!'
            else:
                chosen = True
        if choice == 'q':done = True
        if choice == 'n':newuser()
        if choice == 'e':olduser()
       
if __name__ == '__main__':
    showmenu()

这个程序的主要作用就是熟悉一下字典~