Python running program backwards

Question

I was wondering if a console-based program in python can run backwards. More specifically, while the program runs, if there is a possibility to undo an action from the user input (eg a user accidentally typed sth incorrect and he wants to go back without restarting the program, like tapping Ctrl+Z to undo) Is that possible? If yes how? :)

Answer 1

No.

Unfortunately Python doesn't provide this feature.

Python is an imperative language with mutable state and implementing an "undo" feature would require a quite heavy refactoring of the language internals (after the user types in the wrong input a lot of things can happen in memory... and all of them would have to be in a "transaction" to allow going back to the previous state).

Consider also that when processing the wrong input a program could for example change a file on disk or send a network message to another computer... how do you "undo" these actions?

Answer 2

I doubt that any language has built in support for rolling back arbitrarily in a program. When you see a program with an undo feature it's because that was implemented manually in terms of the specific state that the program manages.