Learning Robotics using Python - Second Edition

Hello_world_subscriber.py

The subscriber code is as follows:

#!/usr/bin/env python 
import rospy 
from std_msgs.msg import String 

The following code is a callback function that is executed when a message reaches the hello_pub topic. The data variable contains the message from the topic, and it will print using rospy.loginfo():

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

The following steps will start the node with a hello_world_subscriber name and start subscribing to the /hello_pub topic:

1. The data type of the message is String, and when a message arrives on this topic, a method called callback will be called:

    def listener(): 
       rospy.init_node('hello_world_subscriber',  anonymous=True) rospy.Subscriber("hello_pub", ...