Can't invoke asyncio event_loop after tornado 5.0 update · Issue #3397 · jupyter/notebook (original) (raw)

On fresh python3.6 venv, after pip install jupyter && jupyter notebook and starting a new python3.6 notebook:

import asyncio

async def foo():
    return 42

asyncio.get_event_loop().run_until_complete(foo())

throws:

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-5-3ad9bf216544> in <module>()
----> 1 asyncio.get_event_loop().run_until_complete(foo())

/usr/local/lib/python3.6/asyncio/base_events.py in run_until_complete(self, future)
    452         future.add_done_callback(_run_until_complete_cb)
    453         try:
--> 454             self.run_forever()
    455         except:
    456             if new_task and future.done() and not future.cancelled():

/usr/local/lib/python3.6/asyncio/base_events.py in run_forever(self)
    406         self._check_closed()
    407         if self.is_running():
--> 408             raise RuntimeError('This event loop is already running')
    409         if events._get_running_loop() is not None:
    410             raise RuntimeError(

RuntimeError: This event loop is already running

If I specify tornado==4.5.3 before pip install jupyter, it works fine