#!/usr/bin/env_python

import rospy
from std_msgs.msg import String

def callback(data):
    rospy.loginfo(rospy.get_caller_id() + "data = %s", data.data)

def listener():
    rospy.init_node('listener', anonymous = True)

    rospy.Subscriber("chatter", String, callback)

    rospy.spin()

if __name__ == '__main__':
    listener()