programming challenge: double words

[ichabod801]

Mine is similar to Yoriz's, but using sets:

def double_words(word_list):
    word_set = set(word_list)
    doubles = set(''.join(pair) for pair in itertools.permutations(word_list, 2) if ''.join(pair) in word_set)
    return [word for word in word_list if word in doubles]

It works on Yoriz's word list. I ran it on the full word list I normally use. It ran quite a while and found 15,876 double words.