Python

None are for formatting. When we refer to formatting, we mostly refer to returning or printing strings in a specific way. isalpha is most likely used for input validation. That is making sure the input is as you would expect, before you proceed with it (or reject the input and don't proceed). split is for taking string apart. It's an incredibly common operation for strings in all languages. You would use it for anything where you need to take a string apart for further analysis. CLI arguments, word counting, even input parsing (imagine user inputs 22,33,44 and you need those numbers in separate variables).