Creating trigrams in Python is very simple trigrams = lambda a: zip(a, a[1:], a[2:]) trigrams(('a', 'b', 'c', 'd', 'e', 'f')) # => [('a', 'b', 'c'), ('b', 'c', 'd'), ('c', 'd', 'e'), ('d', 'e', 'f')] You can generalize this a little bit more ...