class MyQueue():

def __init__(self, value=None):

self.value = value

# 前驱

# self.before = None

# 后继

self.behind = None

def __str__(self):

if self.value is not None:

return str(self.value)

else:

return 'None'

def create_queue():

"""仅有队头"""

return MyQueue()

def last(queue):

if isinstance(queue, MyQueue):

if queue.behind is not None:

return last(queue.behind)

else:

return queue

def push(queue, ele):

if isinstance(queue, MyQueue):

last_queue = last(queue)

new_queue = MyQueue(ele)

last_queue.behind = new_queue

def pop(queue):

if queue.behind is not None:

get_queue = queue.behind

queue.behind = queue.behind.behind

return get_queue

else:

print('队列里已经没有元素了')

def print_queue(queue):

print(queue)

if queue.behind is not None:

print_queue(queue.behind)

if __name__ == '__main__':

queue = create_queue()

push(queue, 1)

push(queue, 2)

push(queue, 3)

push(queue, 4)

print_queue(queue)

print(pop(queue))

print(pop(queue))

print(pop(queue))

print(pop(queue))

print(pop(queue))