I am running Xubuntu 20.04 (after upgrading from 19.04) as a guest on a VirtualBox VM in a Windows 10 host. After an apt install of the jupyter metapackage, I keep getting two errors. To reproduce them, I created a Python3 notebook with the following cells:

[1] import ipywidgets as widgets
[2] widgets.__version__
[3] widgets.IntSlider()

On running cell 1 or on re-opening the notebook the following appears in the terminal where I invoked jupyter notebook:

[IPKernelApp] ERROR | No such comm target registered: jupyter.widget.version

Cells 1 & 2 run fine. Cell 3 creates the widget and the widget seems to operate fine but the notebook and the jupyter notebook terminal show:

[IPKernelApp] WARNING | Widget Javascript not detected.  It may not be installed or enabled properly.

pip3 list (showing only relevant elements) results in:

jupyter-client               6.1.2         
jupyter-console              6.0.0         
jupyter-core                 4.6.3
ipykernel                    5.2.0         
ipython                      7.13.0        
ipython-genutils             0.2.0         
ipywidgets                   6.0.0
nbconvert                    5.6.1         
nbformat                     5.0.4 
notebook                     6.0.3

jupyter nbextension list shows:

  config dir: /home/marvin/.jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK

and after I tried: jupyter nbextension enable --py widgetsnbextension, the following was added:

  config dir: /etc/jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled 
      - Validating: OK

What is the best way of tracking down the problem? Or would I be better off doing one of the following:

  1. re-installing via apt
  2. re-installing via pip3
  3. installing anaconda and re-installing via conda?

Many thanks



I found a workaround and so am answering my own question...

I suspect the problem was that conflicting versions of jupyter-core were installed but I cannot prove this assertion, even when I asked the same question on Launchpad.

My solution was to uninstall all the pip3 and apt components and to delete my local configuration files. Next I installed MiniConda and created appropriate environments for my purposes using Conda. Now everything works perfectly.

(BTW: When using Conda, I recomment using separate environments for each project. If something goes wrong, it is easy to delete and start again and there seems to be less chance of conflicting binary files.)


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