IPKernelApp No such comm: hv-extension-comm / Datashader not displaying visual

I believe that since upgrading to 1.12.0 I’m now getting a warning thrown in the terminal running Jupyter notebook

[IPKernelApp] ERROR | No such comm target registered: hv-extension-comm [IPKernelApp] WARNING | No such comm: hv-extension-comm

I noticed this because I’m having another issue when I run the same code referenced in #3582. Prior to 1.12.0 the Datashader portion of the code ran and displayed but the tools did not, something I believe fixed in this update. However now I’ve upgraded the code…

(datashade(bundled, width=400, height=400, normalization='log') * bundled.nodes).opts( opts.Nodes(size=1, color='celeb',width=800, cmap=colors, legend_position='right')) *\ bundled.select(screen_name='REDACTED').opts(opts.Graph(tools=['hover','zoom_in']), opts.Nodes(fill_color='white'))

…completes without error but does not display the visual. The prior code to display the bundled graph does display properly so it appears related specifically to the datashade function.

I wondered if these could be related and how I might resolve the missing comm.

Many thanks,

[philippjfr]

I don’t think that’s anything to do with HoloViews. Just that other extensions can also raise the same comm error.

On Wed, 23 Sep 2020, 13:48 Jean-Luc Stevens, [e-mail] wrote:

@philippjfr https://github.com/philippjfr An interaction between matplotlib minor versions and comms sounds worrying!

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[stonebig]

just hit by that in an existing notebook, in notebook mode. the notebook clearing is really not enough… but moving to another notebook, not impacted and coming back seems to remove the problem temporarly… Winpython_checker.ipynb.txt