If your wordlist is very long, might it be more efficient to generate all possible 1-letter-differences from ‘word’, then check which ones are in the list? I don’t know any Python but there should be a suitable data structure for the wordlist allowing for log-time lookups.
I suggest this because if your words are reasonable lengths (~10 letters), then you’ll only be looking for 250 potential words, which is probably faster if your wordlist is larger than a few hundred words.