How to calculate continuously data using msg that from subscription, then publish generated data?

[FlamesCN]

I put my code after print func, like this:

async def run(loop):
    nc = NATS()

    await nc.connect("demo.nats.io:4222", loop=loop)

    async def message_handler(msg):
        subject = msg.subject
        reply = msg.reply
        data = msg.data.decode()
        print("Received a message on '{subject} {reply}': {data}".format(
            subject=subject, reply=reply, data=data))
        # MY CODE:
        while True:
              data0 = initial_some_data()
              data1, data2 = calculate_data(data, data0)
              await nc.publish('example', data1)
              data0 = data2
              

    # Simple publisher and async subscriber via coroutine.
    sid = await nc.subscribe("foo", cb=message_handler)

if __name__ == '__main__':
  loop = asyncio.get_event_loop()
  loop.get_debug()
  loop.run_until_complete(run(loop))
  loop.run_forever()

I tried to use 'while True and break' contain my code, that didn't work at all. BTW, I use pandas to calculate data.

[charliestrawn]

There's nothing wrong with the example code, but I wouldn't expect to see any output because you aren't publishing any messages to the subscription. This just connects to nats and listens for messages, but you never send any. If you add something like:

    await nc.publish("foo", b'Hello')
    await nc.publish("foo", b'World')
    await nc.publish("foo", b'!!!!!')

after sid = await nc.subscribe(...) you should see your handler print the messages.

[FlamesCN]

My code was a simple example, the nats-server was published already by another client. I want to know how to keep my code thread-safe in the message_handler, or how to get data out of the coroutine function. Thanks for your answer.