challenge.py

import re

def check_winner(board,row=4):
    try:
        return re.search(r"([^.|])(\1{%d}|%s)"%(row-1,"|".join(r"(.{%d}\1){%d}"%(len(a[0])+d,row-1) for d in range(-1,2))), "|".join("".join(x) for x in a)).group()[0]
    except:
        return "No one"

if __name__ == "__main__":
    a = [
              [".", ".", ".", ".", ".", ".", "."],
              [".", ".", ".", ".", ".", ".", "."],
              [".", ".", "O", ".", ".", ".", "."],
              [".", ".", "X", "O", "X", "X", "."],
              [".", ".", "X", "X", "O", "O", "X"],
              [".", ".", "O", "X", "X", "O", "X"]
        ]
    print "%s wins." % check_winner(a)