#!/usr/bin/env python 
#定義一個列表來模擬棧 
stack = [] 
#進棧,調用列表的append()函數加到列表的末尾,strip()沒有參數是去掉首尾的空格 
def pushit(): 
 stack.append(raw_input('Enter new string: ').strip()) 
#出棧,用到了pop()函數 
def popit(): 
 if len(stack) == 0: 
 print 'Cannot pop from an empty stack!' 
 else: 
 print 'Removed [', stack.pop(), ']' 
#編歷棧 
def viewstack(): 
 print stack 
#CMDs是字典的使用 
CMDs = {'u': pushit, 'o': popit, 'v': viewstack} 
#pr為提示字符 
def showmenu(): 
 pr = """ 
 p(U)sh 
 p(O)p 
 (V)iew 
 (Q)uit 
 Enter choice: """ 
 while True: 
 while True: 
 try: 
 #先用strip()去掉空格,再把第一個字符轉換成小寫的 
 choice = raw_input(pr).strip()[0].lower() 
 except (EOFError, KeyboardInterrupt, IndexError): 
 choice = 'q' 
 print '
You picked: [%s]' % choice 
 if choice not in 'uovq': 
 print 'Invalid option, try again' 
 else: 
 break 
#CMDs[]根據輸入的choice從字典中對應相應的value,比如說輸入u,從字典中得到value為pushit,執行pushit()進棧操作 
 if choice == 'q': 
 break 
 CMDs[choice]() 
#判斷是否是從本文件進入,而不是被調用 
if __name__ == '__main__': 
 showmenu()