Regex match even number of letters

Question

I need to match an expression in Python with regular expressions that only matches even number of letter occurrences. For example:

AAA        # no match
AA                


        

Answer 1

First of all, note that /A*/ matches the empty string.

Secondly, there are some things that you just can't do with regular expressions. This'll be a lot easier if you just walk through the string and count up all occurences of the letter you're looking for.