How to run a program at startup?

[baltika_no_9]

Recent versions of Debian have switched over to systemd, look at how to write a systemd unit for your python script. It's waaaay easier than it used to be with rc files, just a few lines of configuration and a command to enable it.

Yes but a single line in crontab is even easier in my view. It works in any linux system so it isn't a concern if the distro you're using suddenly changes how it wants to handle things.