It wont't handle punctuation, will it? If we pass "Stop Spinning My Words!" we won't get the name of the Kata as it's said in the description.
Your code gives us "Stop gninnipS My !sdroW".

Apart from that, it's very nice and clean solution.

Hi.

What is the point in creating new variable avg? You could just
return sum / array.length;

Regards

You are absolutely right.
My comment was about avoiding unnecessary 'else' statements.
Thanks for the 'anti-pattern', now I got a new word in my vocabulary.

Hi.

You don't need 'else' statement here. It would work like below:

if c == d:
return True
return False

It makes the code a bit cleaner (in my opinion).
Good luck!