Access kernel environment variables from a JupyterLab extension

Question

I have a button extension for JupyterLab.
This extension gives the option to run tools with one click.

I want to show a value from the kernel ENV, let's say 'JOB_NAME' for the opened notebook.

How can I access this ENV variable from the extension TypeScript Code?

Answer 1

Your frontend extension will require a server extension to grab the environment variable Here's a quick example for the handlers.py file:

import json
import os

from jupyter_server.base.handlers import APIHandler
from jupyter_server.utils import url_path_join
import tornado

class RouteHandler(APIHandler):
    # The following decorator should be present on all verb methods (head, get, post,
    # patch, put, delete, options) to ensure only authorized user can request the
    # Jupyter server
    @tornado.web.authenticated
    def get(self):
        actual_key = os.getenv('ENV_VARIABLE')
        self.finish(json.dumps({
            "data": actual_key
        }))


def setup_handlers(web_app):
    host_pattern = ".*$"

    base_url = web_app.settings["base_url"]
    route_pattern = url_path_join(base_url, "serverextension", "get_example")
    handlers = [(route_pattern, RouteHandler)]
    web_app.add_handlers(host_pattern, handlers)

Credit: https://discourse.jupyter.org/t/read-environment-variables-from-jupyter/8878/7