Learn how to use Python’s async functions, threads, and multiprocessing capabilities to juggle tasks and improve the responsiveness of your applications.

And Python’s support for multiprocessing is top-heavy: you have to spin up multiple copies of the Python runtime for each core and distribute your work between them.

I do this all the time. Post the results for each row to a multiprocessing.Queue, and spawn a single process that gets from the queue and writes to the file. It'll post some code when I get to work.