How to Write a Python ROS 2 Node: A Beginner-Friendly Guide

Quick Answer

Learn to create a Python ROS 2 node with our beginner friendly guide. Start building your robotics applications and enhance your programming skills today!

Who This Is For

• ROS 2 Learner
• Robotics Student
• Software Developer

What You Will Learn

• What ROS 2 means in practical robotics.

• How this topic connects to real robot projects.

• What to learn or build next after this article.

• Introduction

• Starting Point

• Learning outcomes

• ROS 2 Python Node High Level Strucutre

• Compiling and Running a ROS 2 node

• ROS 2 Python Publisher Node Understanding

• ROS 2 Python Subscriber Node Understanding

• Single-Node Publishing and Subscribing

• FAQs for ROS 2 Python Nodes

• ROS 2 Python Nodes Quiz

Introduction

Robot Operating System 2 (ROS 2) represents a significant shift in the design and approach to robotic middleware. It's tailored for modern robotics applications, offering

• improved security
• Reliability
• Scalability But this enhancement brought complexity to its structure for starters and introduced a steep learning curve. The key things you need are Python basic syntax understanding.

Starting Point

No understanding of

• ROS 2 python Node Structure
• How to select a message type
• Customize ROS 2 Node template

Learning outcomes

Easily able to

• Publish data on different messages
• Control Publishing messages speed
• Single-Node Publishing and Subscribing

---

ROS 2 Python Node High Level Strucutre

• The below example is taken from the official Wiki of ROS 2 : Writing a simple publisher and subscriber (Python)
• No Need to fully understand the code; just absorb the workflow

1. Importing Libraries

import rclpy
from std_msgs import String

1. Minimal Publisher Class

self.publisher = (msgtype ,topic)
self.timer = run callback function
 every X ms (publish data at a fixed frequency )

1. Call-back function for Publishing

def callback(self){
 msg object create
 msg_data fill in
 publish(msg)

1. Main Function Call

def main(){
rclcpp spin (class)
}

---

Compiling and Running a ROS 2 node

I would recommend you get the publisher - subscriber code and build it according to the wiki. Then we will understand by making changes inside of it.

1. Writing a Python Node

import rclpy
def main():
 rclpy.create node
 node.publish data

1. To compile, we add it into our package, setup.py

entry_points [node]

1. Build the package

colcon build

1. We run using ros2 run command

ros2 run your_package_name node

---

ROS 2 Python Publisher Node Understanding

Code Snippet requires an understanding of Python concepts, but for utilising a basic template for your purpose, you need to just understand four points.

1. Defining which message type to work on Finding ROS 2 Message types

ros2 interface show <name>*( example : ros2 interface show sensor_msgs/msg/Imu )*

1. message on which you want to communicate For astring****data Message

from std_msgs.msg import String

For Integer****data message

from std_msgs.msg import Int32

For IMU sensor data message

from sensor_msgs.msg import Imu

1. Publisher Function call with Topic definition and class member

## For a** string** message
 self.publisher_ = self.create_publisher(String, 'string_topic', 10)
## For a** int32** message
 self.publisher_ = self.create_publisher(Int32, 'int_topic', 10)
## For a** imu sensor** message
 self.publisher_ = self.create_publisher(Imu, 'imu_topic', 10)

1. We have to fill and publishing message data Int32 Data

msg = Int32()
msg.data = count
self.publisher_.publish(msg)

String Data

msg = String()
msg.data = "Hi Robotisim"
self.publisher_.publish(msg)

Imu Sensor data ( this is not a general data like above , it is designed for real imu sensor data carriage )

msg = Imu()
msg.header.stamp = self.get_clock().now().to_msg()
msg.angular_velocity.x = 0.0
msg.angular_velocity.y = 0.0
msg.angular_velocity.z = 1.0
msg.linear_acceleration.x = 0.2
msg.linear_acceleration.y = 0.3
msg.linear_acceleration.z = 0.4
self.publisher_.publish(msg)

---

ROS 2 Python Subscriber Node Understanding

1. The definition of subscriber is dependent on publisher data type and topic name For a string data type

self.subscription = self.create_subscription(String, 'string_topic', self.topic_callback, 10)

1. We have here data type as String
2. Topic name isstring_topic
3. callback function on each message received istopic_callback For Imu data
4. We have here data type as Imu
5. Topic name isimu_topic
6. callback function on each message received istopic_callback

self.subscription_ = self.create_subscription(Imu, 'imu_topic', self.imu_callback, 10)

1. Call back functions to process received data This message type only contains a single entry For Int32

def topic_callback(self, msg):
 self.get_logger().info('I heard: "%d"' % msg.data)

For Imu data

void topic_callback(const sensor_msgs::msg::Imu::SharedPtr msg)
{
 RCLCPP_INFO(this->get_logger(), "Received IMU data: Angular velocity Z: '%f'", msg->angular_velocity.z);
}

There are other fields that you can find through ros2 interface command

---

Single-Node Publishing and Subscribing

There are many cases where we have to subscribe a data as well as publish data within a single node. For that scenario, we apply our programming concepts to ROS 2 Python node.Below is the code that shows the implementation of the concept.you will observe that the additions are in public initialization and private functions We recommend you apply the four-step ROS 2 Python node structure explained initially to the below-listed node.

import rclpy
from rclpy.node import Node
from std_msgs.msg import Int32
from sensor_msgs.msg import Imu
class IntAndIMUPublisherSubscriber(Node):
 def __init__(self):
 super().__init__('int_and_imu_publisher_subscriber')
 self.count_ = 0
 # Publisher for Int32 data
 self.int_publisher_ = self.create_publisher(Int32, 'int_topic', 10)
 # Subscriber for Imu data
 self.imu_subscription_ = self.create_subscription(
 Imu, 'imu_topic', self.imu_callback, 10)
 # Timer to periodically publish Int32 data
 self.timer_ = self.create_timer(1.0, self.timer_callback)
 def timer_callback(self):
 msg = Int32()
 msg.data = self.count_
 self.count_ += 1
 self.get_logger().info('Publishing: %d' % msg.data)
 self.int_publisher_.publish(msg)
 def imu_callback(self, msg):
 self.get_logger().info('Received IMU data: Angular velocity Z: "%f"' % msg.angular_velocity.z)
def main(args=None):
 rclpy.init(args=args)
 node = IntAndIMUPublisherSubscriber()
 rclpy.spin(node)
 node.destroy_node()
 rclpy.shutdown()
if __name__ == '__main__':
 main()

FAQs for ROS 2 Python Nodes

Why should I use Python for ROS 2 development?

• Python is an excellent choice for ROS 2 development due to its simplicity and ease of use. Python allows for rapid development and prototyping, making it ideal for experimenting with new ideas and testing concepts quickly. The extensive range of available libraries and tools in Python further enhances its capabilities, allowing you to implement complex functionalities with minimal code. Python's readability and community support make it a popular choice for beginners and for developing applications that don't require the high performance and real-time capabilities of C++.

How do I handle dependencies and environment setup for ROS 2 Python nodes?

• Managing dependencies and setting up the environment for ROS 2 Python nodes can be done efficiently using virtual environments and package management tools like pip. It is recommended to use a virtual environment to isolate your project's dependencies. You can create a virtual environment and install necessary packages

Can I use Python to develop real-time applications in ROS 2?

• While Python is not inherently designed for real-time applications, it can still be used for certain real-time robotics tasks with careful consideration. Python's Global Interpreter Lock (GIL) can be a limitation for real-time performance, but you can mitigate this by offloading critical real-time tasks to C++ nodes and using Python for higher-level logic and coordination.

ROS 2 Python Nodes Quiz

Practical Example

A practical way to use this article is to connect the concept to a small robot workflow: identify the input, the processing step, and the output you expect from the robot. If the article involves ROS 2, test the idea in a small workspace or simulation before applying it to a larger robot project.

Common Mistakes

• Trying to memorize the term without connecting it to a robot behavior.
• Skipping the prerequisite concepts that make the workflow easier to debug.
• Copying commands or code without checking what each node, topic, file, or parameter is responsible for.
• Treating one tutorial as a complete roadmap instead of linking it to the next concept.

How This Connects to Other Topics

• 3D Printing Robotics Hardware for an Autonomous Robot Build
• How to Collect Raw Sensor Data for Robotics with ROS 2
• How to Add Custom Libraries to a ROS 2 Python Package
• How to Start Developing in ROS 2: A Beginner-Friendly Guide
• How to Finish Your First ROS Robotics Project

Learn Next

• 3D Printing Robotics Hardware for an Autonomous Robot Build
• How to Collect Raw Sensor Data for Robotics with ROS 2
• How to Add Custom Libraries to a ROS 2 Python Package
• How to Start Developing in ROS 2: A Beginner-Friendly Guide
• How to Finish Your First ROS Robotics Project
• ROS 2 Foundation Path

FAQ

Is How to Write a Python ROS 2 Node: A Beginner-Friendly Guide suitable for beginners?

Yes. The article is written to make the concept easier to understand, while still connecting it to practical robotics work.

What should I learn before this topic?

Start with the prerequisite ideas listed in the article, then connect them to a small project or simulation so the concept becomes concrete.

How does this topic connect to real robots?

It helps you understand how software, sensors, control, simulation, or career decisions show up in practical robot development.

What should I do after reading this article?

Pick one related concept from the Learn Next section and build a small example that uses it.

Can I learn this through Robotisim?

Yes. Robotisim connects these concepts to structured learning paths and project-based robotics practice.

Final Summary

How to Write a Python ROS 2 Node: A Beginner-Friendly Guide is part of the broader ROS 2 Learning learning path. The key is to understand the concept, connect it to a real robot workflow, and then practice it through a focused project instead of learning it in isolation.