Empty iterator check

gistfile1.txt

"""
This is useful to avoid throwing empty iterators into a gevent Pool's imap() function, which hangs on empty input.

has_next, maybe_it = iterator_has_next(my_iterator)
if has_next:
   use_the_iterator(maybe_it)
else:
   handle_empty_iterator()
"""

def iterator_has_next(it):
    """ Returns (boolean, iterator?), where iterator is the iterator itself if it has at least one element. """
    try:
        val = it.next()
    except StopIteration:
        return False, None

    def new_it():
        yield val
        for v in it:
            yield v

    return True, new_it()