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

The full answer locates here. Long story short: we can modify Python recipe for itertools.tee function like

from collections import deque


def unzip(iterable):
    """
    Transposes given iterable of finite iterables.
    """
    iterator = iter(iterable)
    try:
        first_elements = next(iterator)
    except StopIteration:
        return ()
    queues = [deque([element])
              for element in first_elements]

    def coordinate(queue):
        while True:
            if not queue:
                try:
                    elements = next(iterator)
                except StopIteration:
                    return
                for sub_queue, element in zip(queues, elements):
                    sub_queue.append(element)
            yield queue.popleft()

    return tuple(map(coordinate, queues))

and then use it

>>> from itertools import count
>>> zipped = zip(count(), count())
>>> xs, ys = unzip(zipped)
>>> next(xs)
0