So I've got a string e.g "AABBCCCASSDSFGDFGHDGHRTFBFIDHFDUFGHSIFUGEGFGNODN".

I want to be able to loop over 16 characters starting and print it. Then move up 1 letter, loop over 16 characters and print that. Until there isn't 16 characters left.

Any help on how i'd do this?

Something like this?

string = "AABBCCCASSDSFGDFGHDGHRTFBFIDHFDUFGHSIFUGEGFGNODN"
for n in range(len(string)-15):print(string[n:n+16])

You have to iterate over every character up to the last character that has 16 characters after it (so the length of the string, minus 15 (because indexing starts at 0) : len(string)-15), and then print the string sliced at that starting index up to the index + 16 (string[n:n+16]).

Slicing is an important and IMO powerful aspect of Python programming, it's a great read if you're new to the language (or programming in general) and you should definitely practice it. The official docs have some good information on the topic.