ROS 2 C++ & Python Learning

Practical examples for exploring rclcpp and rclpy on ROS 2 Jazzy

This repository collects C++ and Python packages designed to illustrate the core concepts of ROS 2: nodes, timers, topics, services, actions, parameters, plugins, TF2, and more. Every example runs on ROS 2 Jazzy; all packages are available in both C++ (rclcpp) and Python (rclpy) implementations.

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Prerequisites

• ROS 2 Jazzy installed and sourced (source /opt/ros/jazzy/setup.bash)
• colcon build tools (python3-colcon-common-extensions)
• rosdep to install system dependencies
• Recommended: Ubuntu 24.04 or another Jazzy-supported OS

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Getting Started

Option 1: Using Docker (Recommended for Quick Setup)

The easiest way to get started is using the provided Docker environment:

# 1. Build the Docker image (one time)
cd docker
chmod +x build_image.sh run_container.sh attach_container.sh
./build_image.sh

# 2. Run the container (mounts repository automatically if ROS2_LEARNING_REPO is set)
export ROS2_LEARNING_REPO=$(pwd)/..  # Set to your repository path
./run_container.sh

# 3. Inside the container: copy packages and build
# If repository was mounted:
cp -r /mnt/ros2_learning/CPP/* ~/ros2_ws/src/
cp -r /mnt/ros2_learning/PYTHON/* ~/ros2_ws/src/

# Or use the helper script:
./helpers/copy_packages.sh /mnt/ros2_learning ~/ros2_ws all

# 4. Install dependencies and build
cd ~/ros2_ws
rosdep install --from-paths src --ignore-src -r -y
colcon build --symlink-install
source install/setup.bash

# 5. Run examples
ros2 run start_with_simple_nodes my_first_node

Note: To open additional terminal sessions in the same container:

# From host (in docker directory)
./attach_container.sh

For detailed Docker instructions, see docker/README.md.

Option 2: Native Installation

If you have ROS 2 Jazzy installed natively:

# create (or reuse) a colcon workspace
mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src

# clone this repository
git clone https://github.com/dottantgal/ROS2_learning.git
cd ROS2_learning
git checkout jazzy

# install dependencies declared in every package.xml
cd ~/ros2_ws
rosdep install --from-paths src --ignore-src --rosdistro jazzy -y

# build everything (C++ + Python packages)
colcon build --symlink-install

# remember to source the workspace before running examples
source install/setup.bash

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Repository Layout

C++ Packages (CPP/)

Each subdirectory is a standalone ROS 2 package with its own CMakeLists.txt and package.xml, so you can copy individual folders into your workspace if preferred.

Folder	Highlights	README
start_with_simple_nodes	First rclcpp::Node examples (free functions vs. classes, timers).	README
publisher_and_subscriber	Minimal publishers/subscribers, custom message type (EmployeeSalary.msg) and class-based nodes.	README
custom_msg_and_srv	Shows how to create and use custom .srv definitions.	README
service_server_and_client	Blocking and asynchronous service clients/servers.	README
parameters	Parameter declaration, retrieval, and updates at runtime.	README
plugins/vehicle_base	Base abstract class for plugin system using pluginlib.	README
plugins/vehicle_plugins	Concrete plugin implementations (Motorbike, Bicycle, Truck).	README
actions/action_tutorial	Action clients/servers, including Jazzy-compliant goal response callback signature.	README
actions/custom_action	Custom action definition (Concatenate.action).	README
message_sync	Synchronising multiple topics with message filters.	README
create_library_with_header/publisher_library	Building a reusable library with header files.	README
create_library_with_header/use_library	Consuming a library from another package.	README
dynamic_tf2_publisher	TF2 broadcaster configurable via parameters, with launch file (launch/tf2_pub.py) and RViz config.	README

Python Packages (PYTHON/)

Python equivalents live under their own packages and install via setup.py. All C++ packages have corresponding Python implementations.

Folder	Highlights	README
start_with_simple_nodes_py	Introductory rclpy nodes (timers, logging, class vs. functional style).	README
publisher_and_subscriber_py	Publisher/subscriber examples, including class-based nodes and exception-aware loops.	README
custom_msg_and_srv_py	Python example nodes using custom services from custom_msg_and_srv.	README
service_server_and_client_py	Service server and client examples in Python.	README
parameters_py	Parameter handling examples in Python.	README
plugins/vehicle_base_py	Base abstract class for Python plugin system using abc module.	README
plugins/vehicle_plugins_py	Concrete plugin implementations using setuptools entry points.	README
actions/action_tutorial_py	Action clients/servers in Python using custom actions from custom_action.	README
message_sync_py	Message synchronization using message_filters in Python.	README
create_library_with_header_py/publisher_library_py	Building a reusable Python library/module.	README
create_library_with_header_py/use_library_py	Consuming a Python library from another package.	README
dynamic_tf2_publisher_py	TF2 broadcaster in Python with launch file support.	README

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Running Selected Examples

C++ Dynamic TF2 Publisher

source install/setup.bash
ros2 launch dynamic_tf2_publisher tf2_pub.py \
  parent_frame:=map child_frame:=base_link x:=1.0 y:=0.0 z:=0.5 yaw:=1.57

The launch file exposes every declared parameter so you can experiment without rebuilding. RViz configuration is available under dynamic_tf2_publisher/dyn_tf2_pub.rviz.

Python Dynamic TF2 Publisher

source install/setup.bash
ros2 launch dynamic_tf2_publisher_py tf2_pub.py \
  parent_frame:=map child_frame:=base_link x:=1.0 y:=0.0 z:=0.5 yaw:=1.57

C++ Publisher Library

The publisher_library package builds a shared library that creates a timed string publisher. The use_library executable links against it:

colcon build --packages-select publisher_library use_library
source install/setup.bash
ros2 run use_library use_library

Python Publisher Library

The publisher_library_py package provides a Python module that creates a timed string publisher. The use_library_py executable uses it:

colcon build --packages-select publisher_library_py use_library_py --symlink-install
source install/setup.bash
ros2 run use_library_py use_library

Python Publisher/Subscribers

colcon build --packages-select publisher_and_subscriber_py --symlink-install
source install/setup.bash
ros2 run publisher_and_subscriber_py simple_publisher_node
ros2 run publisher_and_subscriber_py simple_subscriber_node

C++ Plugin System

colcon build --packages-select vehicle_base vehicle_plugins
source install/setup.bash
ros2 run vehicle_base create_vehicle

Python Plugin System

colcon build --packages-select vehicle_base_py vehicle_plugins_py --symlink-install
source install/setup.bash
ros2 run vehicle_plugins_py create_vehicle

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Key Features

Complete C++ and Python Coverage

Every C++ package has a corresponding Python implementation, allowing you to:

• Compare implementations side-by-side
• Learn both rclcpp and rclpy APIs
• Choose the language that fits your project

Progressive Learning Path

Packages are organized from simple to complex:

1. Basic Nodes - Start here for fundamentals
2. Communication - Publishers, subscribers, services
3. Advanced - Actions, parameters, TF2
4. Architecture - Libraries, plugins, synchronization

ROS 2 Jazzy Compatible

All packages are tested and verified for ROS 2 Jazzy:

• Updated APIs and patterns
• Modern C++17 standard (Jazzy recommendation) and Python 3.8+ support
• Jazzy-specific features and best practices
• Modern parameter API (get_parameter().as_<type>())
• CMake 3.8+ requirement

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Contributing

Issues and pull requests are welcome. If you add a new example, please include:

• A short README snippet describing what learners will gain.
• Required dependencies in package.xml and CMakeLists.txt / setup.py.
• Launch files or test scripts when they add educational value.
• Both C++ and Python implementations when applicable.

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License

TODO: License declaration

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Maintainer

Antonio Mauro Galiano