def argmin_random_tie(seq, fn):
    """Return an element with lowest fn(seq[i]) score; break ties at random.
    Thus, for all s,f: argmin_random_tie(s, f) in argmin_list(s, f)"""
    best_score = fn(seq[0]); n = 0
    for x in seq:
        x_score = fn(x)
        if x_score < best_score:
            best, best_score = x, x_score; n = 1
        elif x_score == best_score:
            n += 1
            if random.randrange(n) == 0:
                best = x
    return best
Return an element with lowest fn(seq[i]) score; break ties at random.
    Thus, for all s,f: argmin_random_tie(s, f) in argmin_list(s, f)