[PyQt] selecting and moving - snapping to grid

[Christopher M. Nahler]

I would like to have the rubberband selection and the moving of objects 
snap to a grid.

 From what I have researched the itemChange method seems to be the way 
to go. I have started with replicating the default behaviour as 
explained in the docu.

def itemChange(self, change, value)
    print change, value
    return value

With the debug info I now see that when I create a new  scene item (in 
my case a rectangle) that this function is visited when I create but not 
when I move the item.

Can anybody help me with info or links with info about how to deal with 
this method?

thanks in advance
Chris