Users can write any valid Python expression (that evals to an int or float) inside Blender's gui number buttons (preceded by #) and have them evaluated to their actual int or float value.
Button Evaluation has access to the same modules as PyDrivers.
For example:
#1.0*9-2.3
#ob("Camera").LocZ
#1.0/ob("Cube").LocX
#math.sin(math.pi) -- or simply #m.sin(m.pi)
etc