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

Why work so hard coming up with a hard to read pattern? Just search for all occurrences of the pattern and count how many you find.

len(re.findall("A", "AbcAbcAbcA")) % 2 == 0

That should be instantly understandable by all experienced programmers, whereas a pattern like "(?

Simple is better.

Answer 2

A* means match "A" zero or more times.

For an even number of "A", try: (AA)+