You can also do

    zip(arr[::3], arr[1::3], arr[2::3])

which is nearly as fast but doesn't work with iterators. If you want to use iterators you could also do

    zip(islice(arr, 0, None, 3), islice(arr, 1, None, 3), islice(arr, 2, None, 3))

which is a tad slower.