I am currently working on a school project. We need to be able to shutdown (and maybe restart) a pythonscript that is running on another raspberry pi using a button.
I thought that the easiest thing, might just be to shutdown the pi from the other pi. But I have no experience on this subject.
I don't need an exact guide (I appreciate all the help I can get) but does anyone know how one might do this?
Well first we should ask if the PI  you are trying to shutdown is connect to a network ? (LAN or the internet, doesn't matter).
If the answer is yes, you can simply connect to your PI through SSH, and call shutdown.sh. 
I don't know why you want another PI, you can do it through any device connected to the same network as your first PI (Wi-Fi or ethernet if LAN, or simply from anytwhere if it's open to the internet). 
You could make a smartphone app, or any kind or code that can connect to SSH (all of them).
Shutdown (a script) one raspberry pi with another raspberry pi