`nwise` and friends!

nwise.py

#!/usr/bin/env python3

from itertools import tee, islice, zip_longest, chain, repeat

nwise = lambda g, *, n=2: zip(*(islice(g, i, None) for i, g in enumerate(tee(g, n))))
nwise_longest = lambda g, *, n=2, fv=object(): zip_longest(*(islice(g, i, None) for i, g in enumerate(tee(g, n))), fillvalue=fv)
first = lambda g, *, n=1: zip(chain(repeat(True, n), repeat(False)), g)
last = lambda g, *, m=1, s=object(): ((xs[-1] is s, x) for x, *xs in nwise_longest(g, n=m+1, fv=s))

if __name__ == '__main__':
  print(
    f"{[*nwise('abcd')] = }",
    f"{[*nwise_longest('abcd')] = }",
    f"{[*first('abcd')] = }",
    f"{[*last('abcd')] = }",
    sep='\n',
  )