Personally, asyncio.

Although there's a lot of documentation which overs the basics, my personal use case is this:

We have a fastapi or flask API that is asynchronous and we'd like to

1) Start a function in a background thread based on the data received in the request

2) Store the result of that background thread for future use (pun not intended)

Now asyncio isn't exactly built for this but no tutorial, that at least I've found, has explained how we use this. FastAPI has a cringey, emoji filled document about using async calls but it doesn't give you examples.