Python 模拟简单的queue

#! /usr/bin/env pythonqueue = []def enQ():    queue.append(raw_input('Enter new string: ').strip())def deQ():    if len(queue) == 0:        print 'Cannot pop from an empty queue!'    else:        print 'Removed [', `queue.pop(0)`, ']'def viewQ():    print queueCMDs = {'e': enQ, 'd': deQ, 'v': viewQ}def showmenu():    pr = """(E)nqueue(D)equeue(V)iew(Q)uitEnter choice: """        while True:        while True:            try:                choice = raw_input(pr).strip()[0].lower()            except (EOFError, KeyboardInterrupt, IndexError):                choice = 'q'            print '\nYou 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()