Python 3, ipywidgets 5.x and kernel names

[benureau]

My code/repo https://github.com/humm/pvlv is using Python 3 and ipywidgets 5.x. This now requires to run
jupyter nbextension enable --py --sys-prefix widgetsnbextension. Failing that, the widgets don't show nor work.

When configuring with a simple requirements.txt file, jupyter 4.1.1 from python 2.7.11 is used, but it correctly launches a Python 3 kernel for the notebooks. However, the jupyter nbextension enable --py --sys-prefix widgetsnbextension command does not work, and widgets throw an error message.

I tried to resolve this with a Dockerfile, but I could not figure out how to switch the entire image to Python 3 properly. I tried using RUN /bin/bash -c "source activate python3", but this is only valid for this line: the next RUN command in the Dockerfile use the 2.7.11 python.

I finally decided to mess with the path: ENV PATH $HOME/anaconda2/envs/python3/bin/:$PATH, which feels a bit icky, but it forces Python 3 on the entire image. And it works for pip too. And... jupyter. So the jupyter that runs the notebook is now the one of python 3.5. More precisely:

The version of the notebook server is 4.2.1 and is running on:
Python 3.5.2 |Anaconda 4.1.1 (64-bit)| (default, Jul  2 2016, 17:53:06) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]

This jupyter has somewhat different kernel names (Python [Root] and Python [python3]), and seems unable to find a match for the notebook kernelspec, which leads to an annoying dialog:

For reference, the kernelspec my notebook is asking for is:

  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },

So the issue is not that problematic, and quite involved. But I feel like there is a quick fix for the kernel matching somewhere. Does anyone with more familiarity with the kernelspec/ipykernel install/jupyter has any idea?

[mbakker7]

Did you come around any fix? I have the exact same problem. Odd.

[benureau]

No, I did not got deeper into the issue. I think this has something to do with different jupyter maintaining different list of kernels, but I did not manage to find clear information about that so far.

[minrk]

This is a bug in the nb_conda_kernels package that is part of Anaconda, and fixed in more recent versions. Updating nb_conda_kernels should fix it.

[mbakker7]

Great! Any idea on how to update? Lots of website on how to install, but
not on how to update.

Thanks, Mark

On Fri, Sep 9, 2016 at 1:40 PM, Min RK notifications@github.com wrote:

This is a bug in the nb_conda_kernels package that is part of Anaconda,
and fixed in more recent versions. Updating nb_conda_kernels should fix it.

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[benureau]

I don't have time to test it right now, but what about:

conda update nb_conda nb_conda_kernels nb_anacondacloud

(from https://groups.google.com/forum/#!topic/jupyter/qE6fCyXe6fs)

[nthiery]

Dear binder / jupyter devs,

I just got what seems to be the same issue. To reproduce, execute the three first cells of:

http://mybinder.org/repo/nthiery/test-binder/

It briefly displays:

Widget Javascript not detected.  It may not be installed properly. Did you enable the widgetsnbextension? If not, then run "jupyter nbextension enable --py --sys-prefix widgetsnbextension"

and the widgets are not displayed.

This was working last week; I noticed the notebook on mybinder was using ipywidgets 4 back then, and now ipywidgets 5. This could be the result result from a change in my setup in the mean time (the repo is now a pip installable package).

Any suggestion on how to fix this? I am happy adjusting my setup.py / requirements.txt. however, since using interacts is a common use case -- and assuming I have not done something stupid -- it would be nice to have them work out of the box.

Thanks in advance!
Nicolas

PS: the above repo is an experiment I did with a friend from earth-sciences; he was amazed by the jupyter+interact+mybinder technology for making his code accessible through interactive web-based forms.