[ros-users] subscribeParam question in rospy

Hey all,

I'm getting started on some work involving Parameter Server, and have a few
quick questions regarding the rospy interface.

According to the documentation of the XMLRPC API, there's a subscription
functionality that I'd like to take advantage of, to avoid polling for
configuration updates:

http://www.ros.org/wiki/ROS/Parameter%20Server%20API

The rospy overview docs don't seem to include this method.

http://www.ros.org/wiki/rospy/Overview/Parameter%20Server

However, looking at the source in paramserver.py, there's clearly the
following method defined:

def subscribe_param(self, key, registration_args)

But it's not clear what the "registration args" tuple is. It seems to end up
at the following call, inside masterdata.py:

def register_param_subscriber(self, param, caller_id, caller_api)

Is there an example somewhere of how to register the appropriate callback to
use subscribeParam from python?

Thanks,

Mike Purvis