asyncio will be running by default with tornado 5

When tornado 5 is released, which is scheduled to be this month, the tornado ioloop will run on asyncio by default. For the most part, this is nice because asyncio will always be running (#9166), but it’s also tricky because simple cells like this that assume asyncio isn’t running will stop working:

loop = asyncio.get_event_loop()
# will fail because loop is already running:
loop.run_until_complete(asyncio.sleep(1))

Without something like #10390, there won’t be an easy way that I can see for users to run asyncio code in IPython, other than putting them in a background thread where they can run it in an eventloop:

aio_pool = ThreadPoolExecutor(1)

def init_loop():
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)
    return loop

aio_loop = aio_pool.submit(init_loop).result()

async def mycoro():
    await asyncio.sleep(1)
    return 5

result = aio_pool.submit(lambda : aio_loop.run_until_complete(mycoro())).result()

and #10390 still needs to handle the fact that asyncio will be running, which I don’t think it does right now.

[fortuna]

It would be great if this was made easier.

I was able to at least find a simpler workaround:

async def do_stuff():
    await asyncio.sleep(1)
    print("Done")

asyncio.run_coroutine_threadsafe(do_stuff(), asyncio.get_event_loop())

[Carreau]

Yes, see https://ipython.readthedocs.io/en/stable/whatsnew/version7.html#ipython-7-0-0

You can just await:

In [1]: import asyncio

In [2]: await asyncio.sleep(1)

In [3]:

And it works.