Round robin with multiple iterators

round_robin_zip.py

def round_robin_zip(*args):
    """
    Make an iterator that aggregates elements from each of the iterables. 
    If the iterables are of uneven length, shorter iterables are re-iterated. 
    Iteration continues until the longest iterable is exhausted.
    
    Derived from itertools.zip_longest().
    """
    iterators =	[iter(it) for it in args]
    orig_iterators = set(iterators)
    while len(orig_iterators) > 0:
        values = []
        for i, it in enumerate(iterators):
            try:
                value = next(it)
            except StopIteration:
                # Remove old iterator from the original set                                
                if it in orig_iterators:
                    orig_iterators.remove(it)
                # Repeat shorter sequences across the longest one                          
                it = iter(args[i])
                iterators[i] = it
                value = next(it)
            values.append(value)
	    if len(orig_iterators) > 0:
            yield tuple(values)