Class Queue

tornado/queues.py:81–346

Coordinate producer and consumer coroutines. If maxsize is 0 (the default) the queue size is unbounded. .. testcode:: import asyncio from tornado.ioloop import IOLoop from tornado.queues import Queue q = Queue(maxsize=2) async def consumer():

class Queue(Generic[_T]):
    """Coordinate producer and consumer coroutines.

    If maxsize is 0 (the default) the queue size is unbounded.

    .. testcode::

        import asyncio
        from tornado.ioloop import IOLoop
        from tornado.queues import Queue

        q = Queue(maxsize=2)

        async def consumer():
            async for item in q:
                try:
                    print('Doing work on %s' % item)
                    await asyncio.sleep(0.01)
                finally:
                    q.task_done()

        async def producer():
            for item in range(5):
                await q.put(item)
                print('Put %s' % item)

        async def main():
            # Start consumer without waiting (since it never finishes).
            IOLoop.current().spawn_callback(consumer)
            await producer()     # Wait for producer to put all tasks.
            await q.join()       # Wait for consumer to finish all tasks.
            print('Done')

        asyncio.run(main())

    .. testoutput::

        Put 0
        Put 1
        Doing work on 0
        Put 2
        Doing work on 1
        Put 3
        Doing work on 2
        Put 4
        Doing work on 3
        Doing work on 4
        Done


    In versions of Python without native coroutines (before 3.5),
    ``consumer()`` could be written as::

        @gen.coroutine
        def consumer():
            while True:
                item = yield q.get()
                try: