My understanding is that what's banned on iOS is not arbitrary code per se, it's arbitrary code downloaded from the internet. Code you enter yourself, like in Pythonista, is just fine.
That's a huge caveat though.
How far does that restriction extend? Can I share or import Pythonista projects from other people?
What's the difference between interpreting a file I downloaded from the Internet and visiting a website?
If you want to split hair, where would you draw the line? Should pythonista go out of the way to prevent copy paste from the browser/email?
Or should apple, being non-arbitrary, also blocks adobe PDF reader since it can open PDFs from the web with javascript just like a browser would do?