How to test Python code through a browser

I run a school that teaches people how to code Python and want to add in an area where people could type in code to be tested. Eg. "Try writing a function that takes x parameters and does y", then they click a button to see if they did it correctly - kind of like Code Academy.

Do you know of any libraries or existing products that would help me to do this? (without starting from scratch). I'm aware that I can use a testing library and set up a server in a VPN that executes the code, but this would be a lot of work to build.