Jupyter Notebook with Python 3.8 - NotImplementedError

Question

Upgraded recently to Python 3.8, and installed jupyter. However, when trying to run jupyter notebook getting the following error:

  File "c:\users\user\appdata\local\programs\python\python38\lib\site-packages\tornado\platform\asyncio.py", line 99, in add_handler
    self.asyncio_loop.add_reader(fd, self._handle_events, fd, IOLoop.READ)
  File "c:\users\user\appdata\local\programs\python\python38\lib\asyncio\events.py", line 501, in add_reader
    raise NotImplementedError
NotImplementedError

I know Python 3.8 on windows switched to ProactorEventLoop by default, so I suspect it is related to this.

Jupyter does not support Python 3.8 at the moment? Is there a work around?

Python 3.8 is very fresh so better go back to 3.7 and wait some time till it will be better tested and modules will be create specially for 3.8. — furas, Oct 17 '19 at 01:06
Possible duplicate of [Jupyter notebook cannot start with python 3.8 in Windows 10](https://stackoverflow.com/questions/54805213/jupyter-notebook-cannot-start-with-python-3-8-in-windows-10) — FObersteiner, Nov 05 '19 at 17:07
This is now fixed in version 6.0.3 of jupyter notebook. Upgrade with `pip install notebook --upgrade` — drec4s, Jan 22 '20 at 12:33

score 201 · Accepted Answer · edited Feb 28 '20 at 06:35

201

EDIT

This issue exists in older versions of Jupyter Notebook and was fixed in version 6.0.3 (released 2020-01-21). To upgrade to the latest version run:

pip install notebook --upgrade

~~Following on this issue through GitHub, it seems the problem is related to the tornado server that jupyter uses.~~

For those that can't wait for an official fix, I was able to get it working by editing the file tornado/platform/asyncio.py, by adding:

import sys

if sys.platform == 'win32':
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())

After the main imports.

I expect an official fix for this soon, however.

edited Feb 28 '20 at 06:35

Udi

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answered Oct 17 '19 at 10:06

drec4s

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Do not expect a fix from Tornado team: https://github.com/tornadoweb/tornado/issues/2608 – Andrew Oct 18 '19 at 09:22
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if you were looking for asyncio.py, take a look at "C:\Python3\Lib\site-packages\tornado\platform" – Bheid Nov 11 '19 at 10:25
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Thanks! If you're using a conda env, Make sure to change the version in the env and not only the global one. Second, make sure you add this change after the `import asyncio` statement :) – Omri374 Nov 20 '19 at 09:37
1

This fixed it for me. In particular: 1. You can get the file location from the stack trace if you run: jupyter -m notebook 2. On my system the file is located here: C:\Users\_NAME_\AppData\Roaming\Python\Python38\site-packages\tornado\platform\asyncio.py – Isaiah Hines Dec 15 '19 at 02:34
This worked for me. If you use virtualenv, this fix needs be applied only to your environment in ENV-DIRECTORY\Lib\site-packages\tornado\platform\asyncio.py – Andi Schroff Jan 13 '20 at 16:31
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This didn't work for me January 2020, Python3.8 but Mirwise Khan's answer below did – Worm Jan 23 '20 at 10:47
I have the latest and it is not fixed. – ProsperousHeart Mar 25 '20 at 20:35
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the 'notebook --upgrade' might fix Jupyter Notebook; however, the tornado/asyncio modification for windows platform is still needed e.g. to [run the latest version of Spyder](https://stackoverflow.com/questions/58557238/spyder-ide-fails-to-start-on-windows-10-with-python-3-8), so you might want to keep the workaround in the answer. – FObersteiner Apr 24 '20 at 05:53
I tried the notebook upgrade, and even delete it and reinstall, but I still got the problem. I finally used the fix in the `tornado\platform\asyncio.py`. – theFrok May 13 '20 at 07:01
may I ask how to update python version **from** 3.7.7 **to** 3.8 via **conda** command or manually within anaconda app on macOS? – Nihat May 13 '20 at 12:41
Tornado 6.0.4, Note that it is still necessary to use asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy()) for this platform/version. https://www.tornadoweb.org/en/stable/releases/v6.0.4.html#general-changes – caoanan Jul 01 '20 at 08:32
Upgrading only jupyter didn't do it for me. I also had to update `ipykernel` seperately. – Mac C. Oct 15 '20 at 13:49
Updating notebook did not work in my case, inserting the code block solved it instead. – Crispy13 Nov 30 '20 at 07:34

score 45 · Answer 2 · edited Feb 02 '20 at 16:11

45

Revising the answer in 2019

Change the end part of the file C:\Users\{USER-NAME}\AppData\Local\Programs\Python\Python38\Lib\asyncio\__init__.py

From

if sys.platform == 'win32':  # pragma: no cover
    from .windows_events import *
    __all__ += windows_events.__all__
else:
    from .unix_events import *  # pragma: no cover
    __all__ += unix_events.__all__

To

import asyncio

if sys.platform == 'win32':
    from .windows_events import *
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
    __all__ += windows_events.__all__
else:
    from .unix_events import *  # pragma: no cover
    __all__ += unix_events.__all__

edited Feb 02 '20 at 16:11

Martijn Pieters

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answered Dec 28 '19 at 15:23

Mirwise Khan

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Both the question and accepted answer were from October 2019 and the solution worked for me – Sundeep Jan 01 '20 at 01:53
2

The accepted answer didn't work for me. this did. Thanks! – Abhishek Agarwal Jan 11 '20 at 04:28
7

Worked for me too, python 3.8 in jan 2020 – fuomag9 Jan 16 '20 at 11:50
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I would **not** go and alter Python's standard library source code. – Martijn Pieters Feb 02 '20 at 16:09
@MartijnPieters make a copy of the file somewhere, try the above solution, if it works > well n good, otherwise just replace the file with old one >> Kinda Win-Win situation – Mirwise Khan Feb 02 '20 at 16:11
1

You can do this **anywhere else**, like in [`site.py`](https://docs.python.org/3/library/site.html). – Martijn Pieters Feb 02 '20 at 16:12
I was having the same issue using Pycharm with Python38 (trying to start localhost:8521 and getting the NotImplementedError) and this solved it. Thank you! – Blank空白 Apr 22 '20 at 08:08

score 3 · Answer 3 · answered Nov 02 '20 at 19:14

3

For me, I had to reinstall asyncio

pip install asyncio --upgrade

And upgrade the kernel package

pip install ipykernel --upgrade

answered Nov 02 '20 at 19:14

penguins

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score 0 · Answer 4 · answered Jul 28 '21 at 06:27

0

I solved this problem by changing the python version from 3.9 to 3.7. (Windows).

answered Jul 28 '21 at 06:27

ming

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Jupyter Notebook with Python 3.8 - NotImplementedError

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