新手学Python 外篇一 队列的实现

queue = []
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 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 '\n 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()