Dan Callahan.py

import json
import re  # Now I have two problems!

def munge(board):
    num_rows = len(board)
    rows = [''.join(row) for row in board]
    cols = [''.join(col) for col in zip(*board)]
    diag1 = [''.join(diag) for diag in
             zip(*[' ' * offset + ''.join(row) for row, offset in
                   zip(board, range(num_rows))])]
    diag2 = [''.join(diag) for diag in
             zip(*[' ' * offset + ''.join(row) for row, offset in
                   zip(board, range(num_rows, -1, -1))])]
    return '|'.join(['|'.join(x) for x in (rows, cols, diag1, diag2)])

def main(blob):
    board = json.loads(blob)
    possibilities = munge(board)
    match = re.search('(X{4}|O{4})', possibilities)
    print "Winner: %s" % (match.group()[0] if match else "None")

if __name__ == '__main__':
    import sys
    main(sys.stdin.read())