example of basic rclpy

ros2_ex.py

import rclpy
import time
import numpy as np
from rclpy.node import Node
from std_msgs.msg import Float32

def main():
    rclpy.init()
    node = Node('my_node')
    rv_publisher = node.create_publisher(Float32, 'my_rv', 1)
    msg_rv = Float32()

    while(True):
        val = np.random.normal(1)
        print("Checking: ", type(val))
        msg_rv.data = val
        rv_publisher.publish(msg_rv)
        time.sleep(0.1)

    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

source /opt/ros/foxy/setup.sh
python ros2_ex.py