Nice. Just a little fixing and polishing: def top_ten(s): words = s.split() return sorted(set(words), key=words.count, reverse=True)[:10]

Nice. Just a little fixing and polishing: def top_ten(s): words = s.split() return sorted(set(words), key=words.count, reverse=True)[:10] (to get the most common words instead of the least).