Hi there,
first compliments for the amazing work everyone did with PTB, it is really well thought through, and very well coded! I have recently started my attempt to integrate the PTB into another application which is already managing the event loop. My intention was to synchronize sending messages on events (which is quite easy using Bot.send_message()) with updating the message queue at the end of every loop. Now without being able to start with Application.run_poll() unless considering going multiple Threads or processes, I was wondering how can I manually get the Application.update_queue to fill and then running the Application.start() to process the queue and get the benefit of the Handlers, without having to write custom code to process the updates.

So far I have managed to use Bot.get_updates() then update the Application.update_queue but when I try to run Application.start() I get a RuntimeError:
RuntimeError: The connection pool was closed while 1 HTTP requests/responses were still in-flight.

In order to initialize the Application outside of the run_poll() context, I have manually used:

try:
  self.application._check_initialized()

except RuntimeError as e:
  print(f"Initializing... {e}")
  await self.application.initialize()

Which seems to execute.

I hope this makes sense, I'll be happy for any advice you can provide.

Best
ANdreaT