A python flask server that runs in the background and can be used in a Google Colab environment

GoogleColabServer.py

## imports
import flask
from flask import Flask
from flask_cors import CORS
from flask_ngrok import run_with_ngrok
import threading
import trace 
import sys
import time

## create Flask app
app = Flask(__name__)
run_with_ngrok(app)
CORS(app)

## a global variable your application can update which the server can provide
## This can easily be replaced by an alternative request to an actual DB to avoid a global variable
YOURDATA = []

@app.route('/data', methods=['GET'])
def get_signals():
    # this is returned to the client - note, it will take data_obj, and convert it to a Javascript object
    data_obj = {
      'data': YOURDATA
    return response

class server_thread_wrapper(threading.Thread): 
  def __init__(self, *args, **keywords): 
    threading.Thread.__init__(self, *args, **keywords) 
    self.killed = False
  def start(self): 
    self.__run_backup = self.run 
    self.run = self.__run       
    threading.Thread.start(self) 
  
  def __run(self): 
    sys.settrace(self.globaltrace) 
    self.__run_backup() 
    self.run = self.__run_backup 
  
  def globaltrace(self, frame, event, arg): 
    if event == 'call': 
      return self.localtrace 
    else: 
      return None
  
  def localtrace(self, frame, event, arg): 
    if self.killed: 
      if event == 'line': 
        raise SystemExit() 
    return self.localtrace 
  
  def kill(self): 
    self.killed = True

def start_server():
  server = server_thread_wrapper(target=app.run)
  server.start()
  return server

def kill_server():
  server.kill()
  server.join()

## start the server
server = start_server()
## temp wait
time.sleep(4)
## show the url to copy to access the server
print("\n\nCopy this address to the Observable notebook!")
! curl -s http://localhost:4040/api/tunnels | jq -r '.tunnels[0].public_url'
## kill the server
# kill_server()