Little help with python
 

Hi, i'm new here.
I'm studying Game programming at AIV in Rome, and in our year program there's a part of Tool Programming with Maya using MEL and Python. there's some things i don't understand in Python yet.
I'm Scripting a plug-in that randomize position, rotation and scale with a UI window, but i don't get what's the problem. i'll post the code below.

it gives me a Runtime error: Lines 30, 36, 42 - Object 0 not found when i push one of the custom buttons.

someone can help me understand? thanks