Code to output the first repeated character in given string?

Question

I\'m trying to find the first repeated character in my string and output that character using python. When checking my code, I can see I\'m not index the last character of my co

Answer 1

Here is a solution that would stop iteration as soon as it finds a dup

>>> from itertools import dropwhile
>>> s=set(); next(dropwhile(lambda c: not (c in s or s.add(c)), letters))
'c'