#!/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 '/nYou 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()