Notebook: Jupyter Notebook throws 'IOLoop' AttributeError with tornado=5.0

[chenchen2015]

Observation

After updating to tornado=5.0 using conda update --all -y, jupyter notebook cannot start and was throwing errors:

$ jupyter notebook& 
[1] 3527                                
Traceback (most recent call last):                                                                  
  File "/home/chenchen2015/anaconda3/bin/jupyter-notebook", line 7, in <module>  
    from notebook.notebookapp import main                                        
  File "/home/chenchen2015/anaconda3/lib/python3.6/site-packages/notebook/notebookapp.py", line 45, in <module>                                                    
    ioloop.install()                    
  File "/home/chenchen2015/anaconda3/lib/python3.6/site-packages/zmq/eventloop/ioloop.py", line 210, in install                                                    
    assert (not ioloop.IOLoop.initialized()) or \                                
AttributeError: type object 'IOLoop' has no attribute 'initialized'              

This was seen on Ubuntu 17.10 with Anaconda 5.1.0 x64.

Solution

Similar to #3397, this is solved by manually downgrading back to tornado=4.5.3 with conda install tornado=4.5.3, hence it seems to be a breaking change caused by tornado 5.0 releases

[takluyver]

You need to upgrade pyzmq to version 17, which is compatible with the new version of Tornado. Anaconda accidentally packaged Tornado 5 before packaging pyzmq 17, but they should have now packaged the latest pyzmq as well.

[chenchen2015]

Good to know, thanks @takluyver

[fterbo]

To be clear, our case was not anaconda, and it was getting everything on a fresh install from pip. We do not install pyzmq or tornado directly (although installing tornado directly did fix it).

[edurand]

Hello,
I'm having ta similar issue with pyzmq == 17.0.0 and tornado == 5.0.1. To be clear, jupyter is indeed able to start with pyzmq updated. However, as soon as starting a new notebook or restarting an old one, I get:
AttributeError: type object 'ZMQIOLoop' has no attribute 'initialized'

Downgrading tornado to 4.5.3 solves the issue.
Thanks

[takluyver]

That probably means that your kernel is running in an environment where you still have an older version of pyzmq, while your notebook is running somewhere with a newer pyzmq.

[edurand]

Thanks - how would I diagnose this?

On Tue, Apr 3, 2018 at 10:20 AM, Thomas Kluyver [e-mail]
wrote:

That probably means that your kernel is running in an environment where
you still have an older version of pyzmq, while your notebook is running
somewhere with a newer pyzmq.

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[takluyver]

Use jupyter kernelspec list to see where your kernelspecs are. That shows you some folders - inside each one should be a kernel.json file pointing to which executable that kernelspec will use.

If there's an entry which ends with ipykernel/resources, then it won't have a kernel.json, and that kernel type will be launched with the same Python that the notebook server runs on.

[edurand]

This is strange, the kernels all point to the right place. All works fine
in a fresh environment, too.

On Tue, Apr 3, 2018 at 10:45 AM, Thomas Kluyver [e-mail]
wrote:

Use jupyter kernelspec list to see where your kernelspecs are. That shows
you some folders - inside each one should be a kernel.json file pointing
to which executable that kernelspec will use.

If there's an entry which ends with ipykernel/resources, then it won't
have a kernel.json, and that kernel type will be launched with the same
Python that the notebook server runs on.

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[wesg52]

I have been having the same issue. I upgraded pyzmq to 17.0.0 globally and the issue has not been solved.

[takluyver]

If you're getting the same traceback as in the original post, then it must be using an older version of pyzmq somewhere. Check for different virtualenvs/conda envs/Python versions.

[khadkakrishna]

thanks, it solved my problem

[ajgpitch]

I followed all the update tornado and pyzmq suggestions, still same error in old conda env. I made a fresh conda env - no error. I made the comparison.

conda install jupyter

fixed my old conda env

[rohannaidu]

Upgrading pyzmq didn't work for me, but as a few other recent comments here have mentioned, downgrading tornado did it!

[jsutch]

Still a problem on OSX 10.13.6 (17G5019) with pip installed latest versions of everything and only the intended versions/environments for pyzmq/tornado/et al. Downgrading tornado to 4.5.3 still works.

[rafiulgits]

Hello,
I'm having ta similar issue with pyzmq == 17.0.0 and tornado == 5.0.1. To be clear, jupyter is indeed able to start with pyzmq updated. However, as soon as starting a new notebook or restarting an old one, I get:
AttributeError: type object 'ZMQIOLoop' has no attribute 'initialized'

Downgrading tornado to 4.5.3 solves the issue.
Thanks