How to unzip an iterator?

Question

Given a list of pairs xys, the Python idiom to unzip it into two lists is:

xs, ys = zip(*xys)

If xys is an iterator,

Answer 1

Suppose you have some iterable of pairs:

a = zip(range(10), range(10))

If I'm correctly interpreting what you are asking for, you could generate independent iterators for the firsts and seconds using itertools.tee:

 xs, ys = itertools.tee(a)
 xs, ys = (x[0] for x in xs), (y[1] for y in ys)

Note this will keep in memory the "difference" between how much you iterate one of them vs. the other.