215 – Implementing pairwise with tee

Before being added to Python 3.10, itertools.pairwise was commonly implemented in terms of itertools.tee:

def my_pairwise(it):
    it1, it2 = tee(it, 2)
    next(it2)
    yield from zip(it1, it2)

This short implementation shows how elegantly the different built-ins and the iterators from itertools can be combined to express new ideas.