I think python is not an app that will execute and open a terminal when the ondemand menu item is pressed.
It would need a menu entry that opens a terminal and then executes python. I think that anyone versed in python will just open a terminal and then enter the python command, whether the extension is onboot or ondemand. And usually python is run from a script anyway.
I don't really see a need for a menu item or icon for python, but if there are a few python users that would like to see it I will put it in.