Python list sorting

In the definition attached I am creating a form out of multiple surface elements.

They are rotated by an exact edge and in that way the form groups of two - two elements together (since its every 3rd edge and they are triangles).

How can I select every first item of each  group of two and rotate it with a different value?

How can I do this in grasshopper components and how can I do it using a python component, I am trying to learn and I am curious of both variations?