Python实现队列的方法

#!/usr/bin/env python 
queue = [] 
def enQ(): 
 queue.append(raw_input('Enter new string: ').strip())
#调用list的列表的pop()函数.pop(0)为列表的第一个元素 
def deQ(): 
 if len(queue) == 0: 
 print 'Cannot pop from an empty queue!' 
 else: 
 print 'Removed [', queue.pop(0) ,']' 
def viewQ(): 
 print queue 
CMDs = {'e': enQ, 'd': deQ, 'v': viewQ} 
def showmenu(): 
 pr = """ 
 (E)nqueue 
 (D)equeue 
 (V)iew 
 (Q)uit 
 Enter choice: """ 
 while True: 
 while True: 
 try: 
 choice = raw_input(pr).strip()[0].lower() 
 except (EOFError, KeyboardInterrupt, IndexError):
 choice = 'q' 
 print '
You picked: [%s]' % choice 
 if choice not in 'devq': 
 print 'Invalid option, try again' 
 else: 
 break 
 if choice == 'q': 
 break 
 CMDs[choice]() 
if __name__ == '__main__': 
 showmenu()