I have a question for ffmpeg. (Python, Django linked)

I have a question about ffmpeg and Python linkage.

ffmpeg is usually run in the command window, for example, file conversion

'ffmpeg -i video.mp4 out1.avi'

The command saves out1.avi to the root path.

But is there a way to put this out1.avi file in a variable with a command like subprocess?

(I want to use url to save it to a designated place, but I'm using s3, so I'm using url to save it There are difficulties. I would appreciate it if you could let me know if there is a way to save it in s3 right away through url!)