python - Notify parent instance about property change -

i have these 2 classes:

class status(object):     def __init__(self):         self._message = ''      @property     def message(self):         return self._message      @message.setter     def message(self, value):         self._message = value   class buddy(object):     def __init__(self, name):         self.name = name         self.status = status()      def status_updated(self):         # should called when self.status.message changed 

and use them this:

buddy = buddy('john') buddy.status.message = 'hello world!'  # should call buddy.status_updated 

i want buddy.status_updated called when modify message property of status. how achieve this?

you'll have store reference back parent; python values not track stored (there can multiple places refer status() instances):

class status(object):     def __init__(self, parent=none):         self._message = ''         self._parent = parent      @property     def message(self):         return self._message      @message.setter     def message(self, value):         self._message = value         if self._parent not none:             self._parent.status_updated()   class buddy(object):     def __init__(self, name):         self.name = name         self.status = status(self)      def status_updated(self):         # should called when self.status.message changed