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python ament cmake

Use ament_cmake to create python package

  • Create ament package
  • Add folder my_cmake_py_pkg
  • Add __init__.py in my_cmake_py_pkg to mark as python module
  • Add node python file my_node.py
  • Set my_node.py as executable
  • Add shabang #!/usr/bin/env python3 in my_node.py
  • Edit to CMakeLists.txt
  • Edit package.xml

Create package

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ros2 pkg create my_cmake_py_pkg --build-type ament_cmake

CMakeLists.txt

CMakeLists.txt
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cmake_minimum_required(VERSION 3.8)
project(my_cmake_py_pkg)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(ament_cmake_python REQUIRED)

# install python package
ament_python_install_package(${PROJECT_NAME})

set(NODES
  my_cmake_py_pkg/my_node.py
)


install(PROGRAMS
    ${NODES}
DESTINATION lib/${PROJECT_NAME}
)


ament_package()

package.xml

Add ament_cmake_python in buildtool_depend

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<buildtool_depend>ament_cmake_python</buildtool_depend>

python nodes

  • Create folder with the package name
  • Create __init__.py in the folder
  • Every node should have #!/usr/bin/env python3 as first line
  • Make the node executable chmod +x my_node.py
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#!/usr/bin/env python3

import rclpy
from rclpy.node import Node

class MyNode(Node):
    def __init__(self):
        node_name="minimal"
        super().__init__(node_name)


def main(args=None):
    rclpy.init(args=args)
    node = MyNode()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

usage

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ros2 run my_cmake_py_pkg my_node.py

VScode tips

Install chmod extension to set handle executable bit on file

chmod extension