Yes, but functions in Python are not that. Mathematical transformations don't support closures for one. Dictionaries are more like functions and indeed I taugh

Yes, but functions in Python are not that. Mathematical transformations don't support closures for one. Dictionaries are more like functions and indeed I taught myself to understand hashmaps as "frozen functions" way back when. You can easily find the set-valued inverse of a function by saying {v: [k for k in d.keys() if k[v]==v] for k, v in d.items()} and that's close to the mathematical definition too.