Unit 4: Exercise 4.2

In this exercise, do we need to create a subscriber that prints odometry message?

Because when I send “roslaunch read_odometry odom_subscriber.py” command on terminal. I don’t get odometry readings. Please advise


You need to fill in the callback and there put a print of the messages recieved.

I believe that’s what I did. Please see the code:

#! /usr/bin/env python

import rospy
from nav_msgs.msg import Odometry

def callback(msg):
print(msg) #This will print the whole Odometry message

       sub = rospy.Subscriber('/odom', Odometry, callback)

That’s what I have. Not sure what you are talking about, callback seems filled and it should print messages received but it doesn’t do it

Lines 12-14 shouldn’t be indented. Because they are, they are part of the callback(msg) function definition.

The callback function gets called whenever the subscriber receives a message. As your code stands right now, the subscriber doesn’t get created until after it was already received a message, which is impossible.


Thank you! I appreciate the help