rosnode name of connected publishers (rospy)

edit

I'm not sure if this is exactly what you're going for, but you can check where each message came from:

def callback(data):
    print data._connection_header['callerid']

For more information, see Section 2.1 here.

Edit:

This information is available if you're willing to interact directly with the rosmaster. I sure hope somebody comes along with a better way to do this! (Building on the example here):

import os
import xmlrpclib
caller_id = '/script'
m = xmlrpclib.ServerProxy(os.environ['ROS_MASTER_URI'])
code, msg, val = m.getSystemState(caller_id)
topic = '/chatter'
if code == 1:
    pubs, subs, srvs = val
    pub_names = [elem[1] for elem in pubs if elem[0] == topic]