tornado >= 5以上がインストールされたjupyter-notebook上でevent_loopを扱うとRuntimeError: This event loop is already runningになる ref: https://qiita.com/sin_tanaka/items/56eb1b8a677fb9b50f7b

file0.txt

import asyncio
from pyppeteer import launch

loop = asyncio.get_event_loop()

async def main():
    browser = await launch()
    page = await browser.newPage()
    await page.goto('http://example.com')
    await page.screenshot({'path': 'example.png'})
    await browser.close()


loop.run_until_complete(main())

file1.txt

---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-16-b0a5d64b1fb0> in <module>()
----> 1 loop.run_until_complete(main())

~/.anyenv/envs/pyenv/versions/3.6.4/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():

~/.anyenv/envs/pyenv/versions/3.6.4/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

file2.sh

$ pip install tornado<=4.5.3
$ pip install jupyter