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##FILL ME IN
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## note =This tutorial assumes you have a working knowledge of compiling programs in ROS and you have completed the [[tf/Tutorials/Introduction to tf | Introduction to tf]] tutorial
## for the canned note of "This tutorial assumes that you have completed the previous tutorials:" just add the links 
## note.0= 
## descriptive title for the tutorial
## title =Writing a tf broadcaster (Python)
## multi-line description to be displayed in search 
## description = This tutorial teaches you how to broadcast the state of a robot to tf.
## the next tutorial description (optional)
## next = Writing a tf listener
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## next.0.link=[[tf/Tutorials/Writing a tf listener (Python)|(Python)]]
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<<IncludeCSTemplate(TutorialCSHeaderTemplate)>>

{{{#!wiki caution
tf is deprecated in favor of [[tf2]]. [[tf2]] provides a superset of the functionality of tf and is actually now the implementation under the hood. If you're just learning now it's strongly recommended to use the [[tf2/Tutorials]] instead.
}}}

<<TableOfContents(4)>>
<<Buildsystem()>>

=== Create package ===
NOTE: Work on this section ONLY IF you haven't done [[http://goo.gl/Bs5vY|Writing a tf broadcaster (C++) tutorial]].

<<Include(tf/Tutorials/Writing a tf broadcaster (C++),,from="##introstart",to="##introend")>>

=== The Code ===
Let's start by making a new directory called `nodes` in our `learning_tf` package.
{{{
$ mkdir nodes
}}}
Fire up your favorite editor and paste the following code into a new file called '''nodes/turtle_tf_broadcaster.py'''.

{{{
#!python block=broadcaster
#!/usr/bin/env python  
import roslib
roslib.load_manifest('learning_tf')
import rospy

import tf
import turtlesim.msg

def handle_turtle_pose(msg, turtlename):
    br = tf.TransformBroadcaster()
    br.sendTransform((msg.x, msg.y, 0),
                     tf.transformations.quaternion_from_euler(0, 0, msg.theta),
                     rospy.Time.now(),
                     turtlename,
                     "world")

if __name__ == '__main__':
    rospy.init_node('turtle_tf_broadcaster')
    turtlename = rospy.get_param('~turtle')
    rospy.Subscriber('/%s/pose' % turtlename,
                     turtlesim.msg.Pose,
                     handle_turtle_pose,
                     turtlename)
    rospy.spin()

}}}
Don't forget to make the node executable: 
 {{{
chmod +x nodes/turtle_tf_broadcaster.py
}}}

=== The Code Explained ===
Now, let's take a look at the code that is relevant to publishing the turtle pose to tf.

<<CodeRef(broadcaster, 19, 19)>>
This node takes a single parameter "turtle", which specifies a turtle name, e.g. "turtle1" or "turtle2".

<<CodeRef(broadcaster, 20, 23)>>
The node subscribes to topic "turtleX/pose" and runs function handle_turtle_pose on every incoming message.

<<CodeRef(broadcaster, 10, 15)>>
The handler function for the turtle pose message broadcasts this turtle's translation and rotation, and publishes it as a transform from frame "world" to frame "turtleX".

== Running the broadcaster ==

Now create a launch file for this demo. With your text editor, create a new file called '''launch/start_demo.launch''', and add the following lines:
{{{
  <launch>
    <!-- Turtlesim Node-->
    <node pkg="turtlesim" type="turtlesim_node" name="sim"/>
    <node pkg="turtlesim" type="turtle_teleop_key" name="teleop" output="screen"/>

    <node name="turtle1_tf_broadcaster" pkg="learning_tf" type="turtle_tf_broadcaster.py" respawn="false" output="screen" >
      <param name="turtle" type="string" value="turtle1" />
    </node>
    <node name="turtle2_tf_broadcaster" pkg="learning_tf" type="turtle_tf_broadcaster.py" respawn="false" output="screen" >
      <param name="turtle" type="string" value="turtle2" /> 
    </node>

  </launch>
}}}
Now you're ready to start your own turtle broadcaster demo:
{{{
 $ roslaunch learning_tf start_demo.launch
}}}
You should see the turtlesim with '''one turtle'''.
<<Include(tf/Tutorials/Writing a tf broadcaster (C++),,from="##checkingstart1",to="##checkingend1")>>
<<Include(tf/Tutorials/Writing a tf broadcaster (C++),,from="##checkingstart2",to="##checkingend2")>>



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## TutorialCategory
## TutorialTurtlesim
## PythonCategory
## LearningCategory