Python核心編程例子userpw

這個程序管理用於登錄系統的用戶信息:登錄名字和密碼。登錄用戶賬號建立後，已存在用戶可以用登錄名字和密碼重返系統。新用戶不能用別人的登錄名建立用戶賬號。

#!/usr/bin/env python
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():
    prompt="""
(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(prompt).strip()[0].lower()
            except (EOFError,KeyboardInterrupt):
                choic='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()