Gets a reference to the current Jupyter Notebook and Server when run inside a Cell (also works for JupyterLab), can map kernel relative paths to files_urls

current_jupyter.py

from pathlib import Path
import re
import requests
from urllib.parse import urljoin

import ipykernel
from notebook.notebookapp import list_running_servers

def files_url_for(kernel_path):
    _server = server()
    path_of_base_url = _server['notebook_dir']
    return urljoin(
      _files_base_url(_server),
      str(Path(kernel_path).resolve().relative_to(path_of_base_url))
    )

def notebook():
    return _current_jupyter()['notebook']

def server():
    return _current_jupyter()['server']

def _files_base_url(server):
    return urljoin(
      server['url'],
       # TODO: this is a hacky whacky assumption... 🤦‍♀️
       # what's the least unprincipled way to do this? 
      f'files/'
    )

def _current_jupyter():
    kernel_id = _current_kernel_id()
    
    return next(( 
        {
          'notebook': notebook,
          'server': server
        }
        for notebook, server in _all_notebooks()
        if notebook['kernel']['id'] == kernel_id
    ))

def _api_url(server, api_name):
  return urljoin(server['url'], f'api/{api_name}')

def _all_notebooks():
  def get_session(server):
    session_url = urljoin(server['url'], 'api/sessions')
    token_param = {
        'token': server.get('token', '')
    }
    sessions_url = _api_url(server, 'sessions')
    return requests.get(sessions_url, token_param).json()

  return (
    ( notebook, server )
    for notebooks, server in ( 
      ( get_session(server), server ) for server in list_running_servers() 
    )
    for notebook in notebooks
  )

def _current_kernel_id():
    connections = ipykernel.connect.get_connection_file()
    return re.search('kernel-(.*).json', connections).group(1)

from .current_jupyter import server, notebook, files_url_for
print(f"URL of the server is: {server()['url']}")
# => 'http://localhost:8888'

print(f"Path of the notebook is: {notebook()}")
# => 'src/noboo.ipynb'

print(f"Frontend URL for 'foobar.txt' is {files_url_for('foobar.txt')}")
# => 'http://localhost:8888/files/foobar.txt'

# maybe we're on jupyterhub, using jupyterlab, logged in as user 'seth'...
# lets say this works: 
f = open('mypath/somefile.txt')
# then you can get a URL to that file that can be used on the frontend like so:
print(f"The URL for path {f.name} is: {files_url_for(f.name)}")
# => 'http://juphub.mydomain.org:8888/user/seth/files/mypath/somefile.txt'