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I updated my conda environment today. Before, I could launch jupyter lab from the terminal. After the updates (which included installing theano, but I'm guessing that's unrelated), I get the following error that I do not understand:

marcel@flaptop:~$ jupyter lab
Traceback (most recent call last):
File "/home/marcel/anaconda3/bin/jupyter-lab", line 7, in <module> from jupyterlab.labapp import main
File "/home/marcel/anaconda3/lib/python3.6/site-packages/jupyterlab/labapp.py", line 7, in <module> from notebook.notebookapp import NotebookApp, aliases, flags  
File "/home/marcel/anaconda3/lib/python3.6/site-packages/notebook/notebookapp.py", line 45, in <module> ioloop.install()
File "/home/marcel/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'

Does anyone know what is going on here?t

serv-inc
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Marcel
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1 Answers1

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Seems to be Tornado version 5. There's discussion here: Install Jupyter Notebook on Miniconda

pip uninstall tornado pip install tornado==4.5.3

fixed it for me, as posted in the link above.

micronaut
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    Thanks! That indeed appears to work. Strange that conda is not on point with their dependencies this time. For the record, I did conda install tornado=4.5.3 rather than your suggestion, but the difference is minor. – Marcel Mar 07 '18 at 11:44
  • I noticed that ipcluster also fails to launch with tornado 5.x, requiring the same downgrade to 4.5.3. – micronaut Apr 12 '18 at 21:25