How can I publish messages on particular timestamps?

edit

In the tutorial pages we have the classical "talker" publisher node

#!/usr/bin/env python
# license removed for brevity import rospy from std_msgs.msg import String

def talker():
    pub = rospy.Publisher('chatter', String, queue_size=10)
    rospy.init_node('talker', anonymous=True)
    rate = rospy.Rate(10) # 10hz
    while not rospy.is_shutdown():
        hello_str = "hello world %s" % rospy.get_time()
        rospy.loginfo(hello_str)
        pub.publish(hello_str)
        rate.sleep()

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

Here, the talker publish a "hello world" at a rate of 10Hz (???). I don't want that. Suppose that I have a text file "time_stamps.txt" that have a set of lines, each one containing a publication timestamp in the form <timestamp seconds> <timestamp nseconds>

I want to publish "hello world" at the rate that my text file specifies. How can I do this?