Matplotlib dynamic plot in ROS2 callback

edit

Hi Guys,

I recently started working on ROS2 and encountered the below issue.

I am trying to plot the points in callback as given in the below code snippet. However this doesn't seem like working.
Could anybody please let me know the right way to plot the points using matplotlib.

Note: I am not getting any errors related to Multi-threading.

    import rclpy
    from rclpy.node import Node

    from std_msgs.msg import String
    from custom_msgs.msg import Custom

    import matplotlib.pyplot as plt 

    global_x_cordinates = []
    global_y_cordinates = []

    class MinimalSubscriber(Node):

        def __init__(self):
            super().__init__('minimal_subscriber')
            self.subscription = self.create_subscription(
                Custom,
                '/custom/custom_topic',
                self.listener_callback,
                10)
            self.subscription  # prevent unused variable warning

        def listener_callback(self, msg):
            #self.get_logger().info('I heard: "%s"' % msg.data.speed_data)

            point_size = len(msg.path)
            print("Number of points : {}".format(point_size))

            x_cordinates = []
            y_cordinates = []

            for each_point in msg.path:
                x_cordinates.append(each_point.x)
                y_cordinates.append(each_point.y)

            global global_x_cordinates 
            global_x_cordinates = x_cordinates

            global global_y_cordinates
            global_y_cordinates = y_cordinates

            plt.plot(global_x_cordinates, global_y_cordinates)

    def main(args=None):
        rclpy.init(args=args)

        minimal_subscriber = MinimalSubscriber()

        plt.show()
        rclpy.spin(minimal_subscriber)

        # Destroy the node explicitly
        # (optional - otherwise it will be done automatically
        # when the garbage collector destroys the node object)
        minimal_subscriber.destroy_node()
        rclpy.shutdown()

    if __name__ == '__main__':
        main()