Manual

Add your dependencies
For this tutorial, we will need to use the rclpy and irobot_create_msgs packages. The rclpy
package allows us to create ROS2 nodes and gives us full access to all the base ROS2
functionality in Python. The irobot_create_msgs package gives us access to the custom
messages used by the Create® 3 for reading the button presses and controlling the lightring.
In package.xml, add these lines under <buildtool_depend>ament_cmake</buildtool_depend>:
<depend>rclpy</depend>
<depend>irobot_create_msgs</depend>
In your .py file, import these packages:
from irobot_create_msgs.msg import InterfaceButtons, LightringLeds
import rclpy
from rclpy.node import Node
from rclpy.qos import qos_profile_sensor_data
Create a class
Now that the dependencies are set, we can create a class that inherits from the rclpy.Node
class. We will call this class TurtleBot4FirstNode.
class TurtleBot4FirstNode(Node):
def __init__(self):
super().__init__('turtlebot4_first_python_node')
Notice that our class calls the super() constructor and passes it the name of our node,
turtlebot4_first_python_node.
We can now create our node in the main function and spin it. Since our node is empty, the node
will be created but it won't do anything.
def main(args=None):
rclpy.init(args=args)
node = TurtleBot4FirstNode()
rclpy.spin(node)
node.destroy_node()
rclpy.shutdown()