def process_event():
       # How to assess a and b variables and invoke
       # foo method specific to that object?
       return /*something */

 class Testing(object):
      def __init__(self, a, b, process_event):
            self.a = a
            self.b = b
            self.process_event_ptr = process_event

      def foo(self)
            return self.a + self.b

 obj1 = Testing(10, 20, process_event)
 obj2 = Testing(100, 200, process_event)
 print obj1.process_event_ptr()
 print obj2.process_event_ptr()