The reason why string[5] = '5' doesn't work is that strings in Python are immutable (cannot be changed). By doing list(string) you are actually creating a new list with the contents of the string and then modifying the list.

I wonder if ChatGPT explains this or just tells you to do this... as this works but can be quite inefficient.

To me this highlights the danger with using AI... sure you can complete a task, but you may not understand why or learn important concepts.