detect when scanner stops

[darter]

I am automating some scanning of old film and would like to know when a scan is complete. There happens to be a green blinking light on the scanner that turns solid when the scanning stops. Maybe use that? Or can I monitor some type of communication between the scanner and my laptop?
I am using Ubuntu 16 and an Epson 4490 slide scanner. Or maybe detect when some type of file writing has completed? Not really sure what to look for here. Any ideas?

[Larz60+]

I think you wanted a different forum.
what does this have to do with python?