Issue with subscriber launch

edit

I am working through tutorials and am having issues with launching my subscriber launch file.

I have created a launch file named odom_subscriber.launch and have the following text in the launch file:

<launch>
    <node pkg="read_odometry" type="odom_subscriber.py" name="odom_sub_node" output="screen" />
</launch>

I have created my python file named odom_subscriber.py and have the following text in it:

    #! /usr/bin/env python

    import rospy

    from nav_msgs.msg import Odometry

    def callback(msg): 

      print msg 

    rospy.init_node('odom_sub_node')

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

rospy.spin()

However, when I try to launch the launch file I get an error. I know I am not subscribing to anything just yet but I wanted to test it to see if all was good at this stage.

To launch the file I used the command:

roslaunch odom_subscriber.launch

I then get the error:

[odom_subscriber.launch] is not a launch file name
The traceback for the exception was written to the log file

Does anyone know where I have gone wrong?