python and world textures

Hi.
Just wondered if someone could confirm for me that setting a current world texture is not possible from a python script. As far as I can tell if

w = Blender.World.Get(‘World’)

then w.textures returns a tuple that I cannot alter. Is there another way? I need to keep with 2.49 for the mo as the rest of my script is quite complex.

Cheers

Ryan