Consider if we have two iterators of different lengths. then we iterate them together one iterator must end up with another iterator.
It will make more sense if we would return a group that containing elements 5 and 6 otherwise it will be problematic.
In this situation, we can use zip_longest().
The python zip_longest() function can fill up the position of empty iterable with some user-defined values.
If the user does not define the fillvalue parameter, the zip_longest() function fills None as the default value.
We can observe in the above example those list y elements are filled with no value.