fix the location /nbextensions ressources in Jupyter

Question

I'm trying to install and run Jupyter on Ubuntu 14.04. The installation seems ok, but when I open a browser and try to open a Python notebook, the browser pops up a window with a Connection Failed title:

A connection to the notebook server could not be established. The notebook will continue trying to reconnect. Check your.network connection or notebook server configuration.

The problem is on the server side: Jupyter does not succeed in locating nbextensions ressources, as indicated by the following warning line:

404 GET /nbextensions/widgets/notebook/js/extension.js

This error has been raised before, but no suggested solution solves it for me. I encounter the same problem on Ubuntu 16.04.

Here is my configuration:

~$ python -V
Python 3.5.3
~$ pip3 -V
pip 9.0.1 from /opt/python3.5/lib/python3.5/site-packages (python 3.5)
~$ jupyter --version
4.2.1
~$ jupyter notebook --version
4.3.2

Here is the Jupyter output on the server:

~$ jupyter notebook --ip=192.168.2.15 --port=8080 --no-browser
[I 15:46:03.317 NotebookApp] Serving notebooks from local directory: /home/foo
[I 15:46:03.318 NotebookApp] 0 active kernels
[I 15:46:03.318 NotebookApp] The Jupyter Notebook is running at: http://192.168.2.15:8080/?token=9df9879c1ce98a4b9bff1c483110a00d08fa1645ec09bdc8
[I 15:46:03.318 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 15:46:03.318 NotebookApp]
    Copy/paste this URL into your browser when you connect for the first time,
    to login with a token:
        http://192.168.2.15:8080/?token=9df9879c1ce98a4b9bff1c483110a00d08fa1645ec09bdc8
[I 15:46:22.058 NotebookApp] Creating new notebook in
[W 15:46:22.645 NotebookApp] 404 GET /nbextensions/widgets/notebook/js/extension.js?v=20170209154602 (161.106.4.5) 10.77ms referer=http://blabla:8080/notebooks/Untitled1.ipynb?kernel_name=python3
[I 15:46:22.749 NotebookApp] Kernel started: c35da40d-1ba0-4680-80f7-b0ab28c3f75c

Answer 1

Need to load nbextensions

Install pip3 install ipywidgets

change file : ~/.jupyter/nbconfig/notebook.json

{
  "load_extensions": {
    "jupyter-js-widgets/extension": true
  }
}

other packages:

pip3 install jupyter-js-widgets-nbextension
pip3 install nbextensions

ReRun the jupyter Notebook

Answer 2

I also had this problem recently on my jupyter notebook

404 GET /nbextensions/widgets/notebook/js/extension.js

with python@3.10 installed from homebrew in a macos with m1. I could not solve as zhi.yang proposed, instead I had to do

jupyter nbextension install --py widgetsnbextension --user
jupyter nbextension enable --py widgetsnbextension --user
jupyter nbextension install --py ipympl --user
jupyter nbextension enable --py ipympl --user

Then I can see it works with

>jupyter nbextension list 
notebook section
 jupyter-matplotlib/extension  enabled 
 - Validating: OK
 jupyter-js-widgets/extension  enabled 
 - Validating: OK

For some reason if I install a python virtual environment, install jupyter, install matplotlib and install ipympl, the widget plots in the notebooks work automatically, without doing the above. This was not the case when I reinstalled python from scratch for my user using homebrew.