Regex to check non-repetition of a set of characters

Question

Suppose I have the set of characters [ABC]. I\'m looking for a regex that would match any permutation of the superset except the empty set, i.e.

Answer 1

This is not something that regular expressions are good at. You might just want to create a list of permutations instead, and then produce all unique substrings.

something like:

def matches(s, characters):
    if len(s) != len(set(s)):
        return False # not unique sequence of characters
    return set(s).issubsetof(set(characters))