iterator pattern every time the cycler reaches the last elementit just starts back at the beginning the third and final function you can look at is zip_longest()which combines set of iterables and returns their matched elements on each iteration zip_longest example import itertools list [ list [' '' '' 'zipped itertools zip_longest(list list print(list(zipped)the result is set of pairs where the first pair contains the first elements of both liststhe second pair contains the second elements of both listsand so on [( ' ')( ' ')( ' ')there are many other interesting things you can do with iteratorsand many of them will help you find simple solutions for tricky problems as is probably the case with most libraries included in the python standard libraryit is worth your effort to explore and master the itertools package generator functions before we begin exploring generator expressionslet' write quick script to demonstrate what they do