Applies function f to all elements in list. Return a iterator of the result. (does not modify the original list)
Note: python 2, map, filter, return a list.
In python 3, they return a iterator object that represent the list.
Applies f to all lists in parallel.
That is, first element of result would be f(e1, e2, e3) where its args are first elemet of each list. f should take same number args as there are lists. All lists must have same number of elements (if short, None is used). Return the new iterator.