Python roundrobin version 2-3 compatible implementation

roundrobin.py

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals

import itertools

def roundrobin(*iterables):
  # https://docs.python.org/3/library/itertools.html
  "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
  # Recipe credited to George Sakkis
  num_active = len(iterables)
  if hasattr(iter([]), 'next'):
    nexts = itertools.cycle(iter(it).next for it in iterables)
  else:
    nexts = itertools.cycle(iter(it).__next__ for it in iterables)
  while num_active:
    try:
      for next_ in nexts:
        yield next_()
    except StopIteration:
      # Remove the iterator we just exhausted from the cycle.
      num_active -= 1
      nexts = itertools.cycle(itertools.islice(nexts, num_active))

print(list(roundrobin('FOO', 'BAR')))  # ['F', 'B', 'O', 'A', 'O', 'R']