#!/usr/bin/env python
     # encoding: utf-8
     #
     # Copyright (c) 2010 Doug Hellmann.  All rights reserved.
     #
     """Show the objects with references to a given object.
     """
     #end_pymotw_header
     
     import gc
     import pprint
     
     class Graph(object):
         def __init__(self, name):
             self.name = name
             self.next = None
         def set_next(self, next):
             print 'Linking nodes %s.next = %s' % (self, next)
             self.next = next
         def __repr__(self):
             return '%s(%s)' % (self.__class__.__name__, self.name)
     
     # Construct a graph cycle
     one = Graph('one')
     two = Graph('two')
     three = Graph('three')
     one.set_next(two)
     two.set_next(three)
     three.set_next(one)
     
     print
     print 'three refers to:'
     for r in gc.get_referents(three):
         pprint.pprint(r)