221 – Generalise pairwise with tee

You can implement a generalisation of itertools.pairwise by using itertools.tee:

from collections import deque
from itertools import islice, tee

def nwise(iterable, n):
    iterators = tee(iterable, n)
    for offset, it in enumerate(iterators):
        deque(islice(it, offset), maxlen=0)
    yield from zip(*iterators)

The call to tee creates n independent iterators.

The loop is used to offset each iterator by a growing number of values that matches the index of the iterator in the list of iterators. You use islice to create this offset and then deque consumes the slice (see the tip 197 about consuming an iterator).

Finally, you zip the misaligned iterators together and use the keyword yield from so that the generator nwise produces the same values as the call to zip.