KevsRobots Learning Platform
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By Kevin McAleer, 2 Minutes
touch my_py_pkg/sub.py
chmod -R 777 my_py_pkg
This will create the new empty file, and fix the permissions so we can write to it from VS Code.
Cut and paste the following code into the new file:
import rclpy
from rclpy.node import Node
from std_msgs.msg import String
class Listener(Node):
def __init__(self):
super().__init__("node_test")
self.counter_ = 0
# create_subscriber needs 3 parameters: Msg Type, topic name, the callback, and queue size buffer
self.subscriber = self.create_subscription(String, "Hello", self.callback_hello, 10)
self.get_logger().info("Subscribed to Hello topic")
def callback_hello(self, message):
self.get_logger().info(message.data)
def main(args=None):
rclpy.init(args=args)
node = Listener()
rclpy.spin(node)
rclpy.shutdown()
if __name__ == "__main__":
main()
We now need to update setup.py to include the entry_point for our code. An entry point is the name of the python scripts that are available to run from with the package, and are shown in the list when you type ros2 run my_py_pkg.
my_py_pkg folderentry_points={
'console_scripts' : [
"pub = my_py_pkg.pub:main",
"talker = my_py_pkg.talker:main",
"listener = my_py_pkg.sub:main"
],
},
We can now build out package using colcon build. Do this from the root of the workspace (in this case /ros2/my_py_pkg):
cd /ros2/my_py_pkg
colcon build
source install/setup.bash
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