@bestwebua, it's valid Python code.
@Sydchill, Please don't mark a problem in your code as an issue.
Btw, the code looks like it should pass; did you try re-submitting as shown in the description?

Holyshit! What is 'elif'???? Don't use and/or in boolean conditions.

This is not a Kata error, it is a problem in your code.

You are receiving that error when the input is an empty string because you are trying to access an index that doesn't exist.

The second problem with your code is that it needs to consider capital letters and non-capital letters as the same character. That means that "abcdeaB" should be equal to 2 since there are 2 "B"s (not considering the casing).