Efficiently build a graph of words with given Hamming distance

Question

I want to build a graph from a list of words with Hamming distance of (say) 1, or to put it differently, two words are connected if they only differ from one letter (lo

Answer 1

There's no need to take a dependency on the alphabet size. Given a word bot, for example, insert it into a dictionary of word lists under the keys ?ot, b?t, bo?. Then, for each word list, connect all pairs.

import collections


d = collections.defaultdict(list)
with open('/usr/share/dict/words') as f:
    for line in f:
        for word in line.split():
            if len(word) == 6:
                for i in range(len(word)):
                    d[word[:i] + ' ' + word[i + 1:]].append(word)
pairs = [(word1, word2) for s in d.values() for word1 in s for word2 in s if word1 < word2]
print(len(pairs))