Insert the string into a list? Like this?
'hello' -> ['hello']
or this? (but that’s not what you said)
['h', 'e', 'l', 'l', 'o']
And, what difference would this make to the operation that you’re planning to do? Which operation is that exactly anyway?
Append means to add at the end. You can assign to slices, yes, but you’d be overwriting those elements and would therefore need to first make a list that is of the new size and space out the elements, you could just as well space them out with
There doesn’t exist space between elements in a list. You can’t drop values in between existing values. You need a new list, or a different data structure (if you can imagine it and describe it well enough, then you can also write that code - to write code is to describe what you want to happen)
str’s join method already does exactly what you’re asking for.
If you think something seems likely to exist, then it’s probably fairly simple to google it. But if you’re guessing rather wildly, or wishing, then the approach you should be taking is probably instead to learn the language features and then using those to describe what you want to do.
In this case I think the reasonable train of thought is that, since each letter has to be processed, a loop is needed. And as each character is iterated over, you would keep that character somewhere, and add an X after it. A list supports this well, and also easily supports removing the last X at the end. Once the iteration is done, create a string from those characters, something that str.join does. (and if one isn’t aware of str.join then googling will make it easy to figure out how to convert a list of characters into a string)