How do i rotate along local axis ?

Hello:
I 'd like to be able to rotate an object (in fact many of them) along one of is axis.
But the RotY and RotY attributes aren’t that easy to use.

If i use :

obj.RotY=Obj.RotY+25

then my object won’t rotate along its Y axis but along some strange mathematically -founded-mystery-axis.
Same for the Z axis. Only X is straightforward.
So this simple question:

How do i do to have an object rotate n degrees along its (local) Y axis for instance ???

I hope that someone else can give you a better answer… but I have a Python class that can do rotations around any global/local/arbitrary axis and global/local origin, in any combination. You can use getmatrix and setmatrix to convert between Blender and the Python class.