How to get the last letter in a string that is not a specific character using regex?

This is a related question but doesn’t specifically have the answer I’m looking for. How to search for the last occurrence of a regular expression in a string in python?

Essentially, say for input "iuasgjjgg", I want to find the rightmost character that is not "j".

So

solution("abcdefghijh") => 10 (because h is at index 10)

solution("hhhjjjhhh") => 8 (because last h is at index 8)

the fact that it is "h" is not important, it’s just important that it’s not "j"

I think it has something to do with re.search and negative lookaheads but I’m having trouble putting everything together.

edit: also I know that this is probably possible using a naive approach but I’m looking for a regex solution.

>Solution :

One approach would be to rstrip the letter j, and then take the final remaining character:

inp = ["abcdefghijh", "hhhjjjhhh"]
last = [x.rstrip('j')[-1] for x in inp]
print(last)  # ['h', 'h']

If instead you want the final index of the above characters, just take the length:

inp = ["abcdefghijh", "hhhjjjhhh"]
last = [len(x.rstrip('j')) - 1 for x in inp]
print(last)  # [10, 8]