In Python 3’s itertools there is a function called zip_longest. It should do the same as izip_longest from Python 2.
Why the change in name? You might also notice that itertools.izip is now gone in Python 3 – that’s because in Python 3, the zip built-in function now returns an iterator, whereas in Python 2 it returns a list. Since there’s no need for the izip function, it also makes sense to rename the _longest variant for consistency.