After update to 0.9.0: "Error displaying widget: model not found"

[Dommsko]

Hello,

I set up a TLJH last year to deploy interactive learning material for students created using ipycanvas. However, after updating to 0.9.0 and ipywidgets to 7.6.3 I can not display canvases anymore. This minimal example is already throwing an error:

from ipycanvas import Canvas
c = Canvas(width=200, height=200)
c

Error displaying widget: model not found

Did I miss some change in the syntax or could there be a conflict with versions. I googled the error message and just found something about incompatibilities between (other) Jupyter libraries.

$ pip freeze

alembic==1.4.3
asn1crypto==0.24.0
async-generator==1.10
attrs==20.2.0
backcall==0.2.0
bleach==3.2.1
certifi==2020.6.20
certipy==0.1.3
cffi==1.12.3
chardet==3.0.4
conda==4.8.1
conda-package-handling==1.3.11
cryptography==2.7
decorator==4.4.2
defusedxml==0.6.0
entrypoints==0.3
idna==2.8
import-ipynb==0.1.3
importlib-metadata==2.0.0
ipycanvas==0.9.0
ipykernel==5.3.4
ipython==7.18.1
ipython-genutils==0.2.0
ipywidgets==7.6.3
jedi==0.17.2
Jinja2==2.11.2
json5==0.9.5
jsonschema==3.2.0
jupyter-client==6.1.7
jupyter-core==4.6.3
jupyterhub==1.0.0
jupyterlab==2.2.9
jupyterlab-pygments==0.1.2
jupyterlab-server==1.2.0
jupyterlab-widgets==1.0.0
libarchive-c==2.8
Mako==1.1.3
MarkupSafe==1.1.1
mistune==0.8.4
nbclient==0.5.1
nbconvert==6.0.7
nbformat==5.0.8
nbgitpuller==0.7.2
nbresuse==0.3.6
nest-asyncio==1.4.2
notebook==6.0.3
nteract-on-jupyter==2.1.3
numpy==1.19.2
oauthlib==3.1.0
packaging==20.4
pamela==1.0.0
pandocfilters==1.4.3
parso==0.7.1
pexpect==4.8.0
pickleshare==0.7.5
Pillow==8.0.1
prometheus-client==0.8.0
prompt-toolkit==3.0.8
psutil==5.7.3
ptyprocess==0.6.0
pycosat==0.6.3
pycparser==2.19
Pygments==2.7.2
pyOpenSSL==19.0.0
pyparsing==2.4.7
pyrsistent==0.17.3
PySocks==1.7.0
python-dateutil==2.8.1
python-editor==1.0.4
pyzmq==19.0.2
requests==2.22.0
ruamel-yaml==0.15.46
Send2Trash==1.5.0
six==1.12.0
SQLAlchemy==1.3.20
terminado==0.9.1
testpath==0.4.4
tornado==5.1.1
tqdm==4.32.1
traitlets==5.0.5
urllib3==1.24.2
wcwidth==0.2.5
webencodings==0.5.1
widgetsnbextension==3.5.1
zipp==3.4.0

I would really appreciate any support on this topic and would gladly help out with additional information. Thanks in advance!

Kind regards,
Dominik

[martinRenou]

Can you run jupyter labextension list

[Dommsko]

Can you run jupyter labextension list

Hello Martin,

thanks for your fast response. Quicker than I could have a lunch break :-) I thought that Jupyter Lab would remember its extensions but your guess was correct:

$ jupyter labextension list
JupyterLab v2.2.9
Known labextensions:
   app dir: /opt/tljh/user/share/jupyter/lab
        @jupyter-widgets/jupyterlab-manager v2.0.0  enabled  OK

I simply rebuilt ipycanvas and it got fixed.

$ jupyter labextension install @jupyter-widgets/jupyterlab-manager ipycanvas
$ jupyter labextension list
JupyterLab v2.2.9
Known labextensions:
   app dir: /opt/tljh/user/share/jupyter/lab
        @jupyter-widgets/jupyterlab-manager v2.0.0  enabled  OK
        ipycanvas v0.9.0  enabled  OK

It is working now and I even have the feeling that my animations are running a lot smoother now. Thanks a lot!

Kind regards,
Dominik

[martinRenou]

Cool! Happy you could fix it.

Yeah, ipycanvas had a couple of performance improvements in latest releases.

[Dommsko]

Glad to see that the project is still active. Thanks a lot for your great work!