[Closed] Keep the position key for the first and the last frame

Hi , i wrote a script that kills the position or/and rotation or/and scale for selected objects ,what i want to know is how can i keep for example the postion key for the first and the last frame of selected objects.
Here’s a piece from the code i wrote:

        on trsf pressed do 
            (
            for i in selection do deleteKeys i.pos.controller
            )
        on rot pressed do 
            (
            for i in selection do deleteKeys i.rotation.controller
            )
        on scl pressed do 
            (
            for i in selection do deleteKeys i.scale.controller

The objects don’t have the same animation lenght.
Thanks!