That’s what I do:
def myClicker():
print "event: ", event
print "event.current_element: ", event.current_element
print "event.type: ", event.type
print "event.parameters: ", event.parameters
myBut = doc.GetElementById("myclickerbutton")
myBut.AddEventListener("click", myClicker)
As stated here http://librocket.com/wiki/documentation/PythonManual/Events, the event handler that is called has three global variables: event, document and self