JupyterLab 3 troubleshooting

Running a Flask application and serving it to JupyterLab

You are able to run a Flask webserver application and make it visible in JupyterLab.

Components you need:

• Install nodejs from conda

  • nodejs is needed for commands such as jupyter labextension install and jupyter lab build. You might need to install a specific version of nodejs depending on the JupyterLab version. Currently version >=12.0.0 is required.

• Install the jupyter-server-proxy extension.

• Flask version >= 2.2.0 is suggested.

Potential further useful tools:

• We suggest also looking at the jupyterlab_iframe extension.

Modify your flask application code

Make sure you add the following snippet to your flask application code:

from werkzeug.middleware.proxy_fix import ProxyFix
from werkzeug.middleware.dispatcher import DispatcherMiddleware
from werkzeug.wrappers import Response

# ...
# your code goes here
# ...


app.wsgi_app = DispatcherMiddleware(
     Response('Not Found', status=404),
     {'/proxy/absolute/5000': ProxyFix(app.wsgi_app)})