Consume multiple iterators, filling each when exhausted with the last value they produced.

zip_longest_last.py

def zip_longest_last(*args):
	"""Consume multiple iterators, filling each when exhausted with the last value they produced."""
	line = []
	# CREATE a list of iterators of iterable objects passed as args.
	iters = [iter(it) for it in args]
	active = len(iters)
	lasts = [None]*active
	# CREATE a generator that yields the last item forever.
	def take_last(index):
		while True:
			yield lasts[index]
	# MAIN LOOP.
	while True:
		# FOREACH iterator in the list.
		for n, it in enumerate(iters):
			try:
				# GET the value from the iterator.
				value = next(it)
			# CHECK if there are no elements left into the iterator.
			except StopIteration:
				# REPLACE the exhausted iterator with the generator
				# that yields forever the last element.
				iters[n] = take_last(n)
				# SET that last element to the value we have to yield.
				value = lasts[n]
				# DECREASE active iterators.
				active -= 1
				if active == 0:
					# EXIT if there are no more active iterators.
					return
			else:
				# SAVE the last element of this iterator.
				lasts[n] = value
			# ADD this element value to the current line of elements
			# we will yield.
			line.append(value)
		# YIELD the line of elements as a tuple.
		yield tuple(line)
		# CLEAR the line to make room for the next line.
		line = []

Thanks! 👍