Failed to load model class 'Cube3DModel' from module 'lexcube'

[f-tonini]

Tried installing lexcube on my Jupyter notebook using pip install. Restarted the kernel, but when trying to visualize a Zarr cube, I keep getting an error message:

[Open Browser Console for more detailed log - Double click to close this message]
Failed to load model class 'Cube3DModel' from module 'lexcube'
Error: No version of module lexcube is registered

Not sure what else to try given that I restarted the Kernel and also restarted and verified lexcube was installed correctly.

[f-tonini]

import xarray as xr
import lexcube
ds = xr.open_dataset("random_data.zarr", chunks={}, engine="zarr")
da = ds["air_temperature"][:,:,:]
w = lexcube.Cube3DWidget(da,cmap="thermal_r", vmin=-20, vmax=30)
w

[msoechting]

Hi Francesco, unfortunately (due to the overall software architecture) the error message gives no detail on what went wrong. Could you please provide:

1. your Python version,
2. the output from pip list from your environment,
3. any error messages appearing in your browser console when that error appears (Windows/Linux: press F12)?

[f-tonini]

Hi!

1. I am using python version 3.12.*
2. Output from pip list:

aiohappyeyeballs 2.6.1
aiohttp 3.13.3
aiosignal 1.4.0
anyio 4.12.1
argon2-cffi 25.1.0
argon2-cffi-bindings 25.1.0
arrow 1.4.0
asttokens 3.0.1
async-lru 2.1.0
attrs 25.4.0
babel 2.17.0
beautifulsoup4 4.14.3
bleach 6.3.0
Bottleneck 1.6.0
cachey 0.2.1
certifi 2026.1.4
cffi 2.0.0
cftime 1.6.5
charset-normalizer 3.4.4
click 8.3.1
cloudpickle 3.1.2
comm 0.2.3
dask 2026.1.1
debugpy 1.8.19
decorator 5.2.1
defusedxml 0.7.1
donfig 0.8.1.post1
executing 2.2.1
fastjsonschema 2.21.2
fqdn 1.5.1
frozenlist 1.8.0
fsspec 2026.1.0
google-crc32c 1.8.0
h11 0.16.0
HeapDict 1.0.1
httpcore 1.0.9
httpx 0.28.1
idna 3.11
ipykernel 7.1.0
ipython 9.9.0
ipython-genutils 0.2.0
ipython_pygments_lexers 1.1.1
ipywidgets 7.8.3
isoduration 20.11.0
jedi 0.19.2
Jinja2 3.1.6
json5 0.13.0
jsonpointer 3.0.0
jsonschema 4.26.0
jsonschema-specifications 2025.9.1
jupyter_client 8.8.0
jupyter_core 5.9.1
jupyter-events 0.12.0
jupyter-lsp 2.3.0
jupyter_server 2.17.0
jupyter_server_terminals 0.5.4
jupyterlab 4.5.2
jupyterlab_pygments 0.3.0
jupyterlab_server 2.28.0
jupyterlab_widgets 1.1.11
lark 1.3.1
lexcube 1.0.3
locket 1.0.0
MarkupSafe 3.0.3
matplotlib-inline 0.2.1
mistune 3.2.0
multidict 6.7.0
nbclient 0.10.4
nbconvert 7.16.6
nbformat 5.10.4
nest-asyncio 1.6.0
netCDF4 1.7.4
notebook 7.5.2
notebook_shim 0.2.4
numcodecs 0.16.5
numpy 2.4.1
opencv-python-headless 4.13.0.90
packaging 26.0
pandas 3.0.0
pandocfilters 1.5.1
parso 0.8.5
partd 1.4.2
pexpect 4.9.0
pip 25.3
platformdirs 4.5.1
prometheus_client 0.24.1
prompt_toolkit 3.0.52
propcache 0.4.1
psutil 7.2.1
ptyprocess 0.7.0
pure_eval 0.2.3
pycparser 3.0
Pygments 2.19.2
python-dateutil 2.9.0.post0
python-json-logger 4.0.0
PyYAML 6.0.3
pyzmq 27.1.0
referencing 0.37.0
requests 2.32.5
rfc3339-validator 0.1.4
rfc3986-validator 0.1.1
rfc3987-syntax 1.1.0
rpds-py 0.30.0
Send2Trash 2.1.0
setuptools 80.10.1
six 1.17.0
soupsieve 2.8.3
stack-data 0.6.3
terminado 0.18.1
tinycss2 1.4.0
toolz 1.1.0
tornado 6.5.4
traitlets 5.14.3
typing_extensions 4.15.0
tzdata 2025.3
uri-template 1.3.0
urllib3 2.6.3
wcwidth 0.3.0
webcolors 25.10.0
webencodings 0.5.1
websocket-client 1.9.0
wheel 0.45.1
widgetsnbextension 3.6.10
xarray 2025.12.0
yarl 1.22.0
zarr 3.1.5

3. It does not appear that the browser will let me inspect an element inside a notebook cell with that error as it may not expose it to the front end elements. Any other way to get what you need?

I am setting up this environment by using a simple env.yml file configured as follows:

name: lexcube-hack
channels:

• conda-forge
  dependencies:
• python=3.12.*
• pip
• pip:
  • lexcube

[msoechting]

Hi Francesco, unfortunately I am not able to reproduce your issue 😕 I have created a virtual environment (not conda but python -m venv .venv) with your packages under Python 3.11 and Windows, and running Lexcube in jupyter lab with your code works just fine. Can you try using venv instead of conda or with a different data set to see if that works for you? For the web console output, no "inspect element" is needed, the error should be in the console output (F12 -> "Console" or something along those lines).

[f-tonini]

Hello, what I see in the browser console output when running that code cell is:

327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1 Error: Module @jupyter-widgets/base, version ^1.2.0 is not registered, however, 2.0.0 is
at f.loadClass (446.f8696ce72124c78273da.js?v=f8696ce72124c78273da:1:75487)
at f.loadModelClass (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:10580)
at f._make_model (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:7368)
at f.new_model (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:5137)
at f.handle_comm_open (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:3894)
at push.1446.constructor._handleCommOpen (446.f8696ce72124c78273da.js?v=f8696ce72124c78273da:1:73903)
at b._handleCommOpen (jlab_core.d25e823c058f4ae79a91.js?v=d25e823c058f4ae79a91:1:1372274)
at async b._handleMessage (jlab_core.d25e823c058f4ae79a91.js?v=d25e823c058f4ae79a91:1:1374264)
loadModelClass @ 327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1
327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1 Error: No version of module lexcube is registered
at f.loadClass (446.f8696ce72124c78273da.js?v=f8696ce72124c78273da:1:75366)
at f.loadModelClass (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:10580)
at f._make_model (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:7368)
at f.new_model (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:5137)
at f.handle_comm_open (327.d242f1a99504b2d5b629.js?v=d242f1a99504b2d5b629:1:3894)
at push.1446.constructor._handleCommOpen (446.f8696ce72124c78273da.js?v=f8696ce72124c78273da:1:73903)
at b._handleCommOpen (jlab_core.d25e823c058f4ae79a91.js?v=d25e823c058f4ae79a91:1:1372274)
at async b._handleMessage (jlab_core.d25e823c058f4ae79a91.js?v=d25e823c058f4ae79a91:1:1374264)

The reason we are using conda rather than a venv was because we are using an environment.yml file with all the packages we want installed at once to create the environment for Jupyter Lab...

[msoechting]

It seems there is an issue with a depending package: @jupyter-widgets/base, version ^1.2.0 is not registered, however, 2.0.0 is Lexcube requires ipywidgets==7.8.3 which in turn requires @jupyter-widgets/base to be ^2 || ^3 || ^4 . I have no clue why your environment is looking for version 1.2. Maybe your environment is using an outdated jupyter lab version? Or something else is going wrong in the dependency resolving chain?