Can't find module when loading Jupyter Server Extension

Question

I want to load a Jupyter Notebook Server Extension within a local directory:

server_ext/
|__  __init__.py
|__  extension.py

extension.py

from notebook.utils import url_path_join
from notebook.base.handlers import IPythonHandler

class HelloWorldHandler(IPythonHandler):
    def get(self):
        self.finish('Hello, world!')

def load_jupyter_server_extension(nbapp):
    """
    nbapp is istance of Jupyter.notebook.notebookapp.NotebookApp
    nbapp.web_app is isntance of tornado.web.Application - can register new tornado.web.RequestHandlers
    to extend API backend.
    """
    nbapp.log.info('My Extension Loaded')
    web_app = nbapp.web_app
    host_pattern = '.*$'
    route_pattern = url_path_join(web_app.settings['base_url'], '/hello')
    web_app.add_handlers(host_pattern, [(route_pattern, HelloWorldHandler)])

I run the following command from the directory containing server_ext:

jupyter notebook --NotebookApp.server_extensions="['server_ext.extension']"

But I get the error "No module named extension". Is there something I have to do to get Jupyter/python session to recognize the path to the module?

Answer 1

Figured it out-

it turns out that Jupyter Notebook's call to importlib.import_module sets package=None, which means that relative paths will not work.

As a workaround, the ~/.jupyter/jupyter_notebook_config.py script can be modified to append your local directory to the PYTHONPATH so that the module can be found.

import sys
sys.path.append("C:\\Users\\eric\\server_ext")

c.NotebookApp.server_extensions = [
    'extension'
]