Simple Publisher Using Rospy

talker.py

#!/usr/bin/env python
import roslib; roslib.load_manifest('beginner_tutorials')
import rospy
from std_msgs.msg import String

def talker():
        pub = rospy.Publisher('chatter', String)
        rospy.init_node('talker')
        while not rospy.is_shutdown():
                #subtitute the time to message
                str="Hello ROS World %s" % rospy.get_time()
                #loginfo()
                #gets the message printed to screen
                #gets it written to the Node's log file
                #gets it written to rosout
                rospy.loginfo(str)
                pub.publish(String(str))
                rospy.sleep(1.0)

if __name__== '__main__':
        try:
                talker()
        except rospy.ROSInterruptException:pass