Add example for migrating a Python package from ROS 1 to 2

source/How-To-Guides/Migrating-from-ROS1.rst

@@ -12,6 +12,7 @@ If you are new to porting between ROS 1 and ROS 2, it is recommended to read thr
    Migrating-from-ROS1/Migrating-Interfaces
    Migrating-from-ROS1/Migrating-CPP-Package-Example
    Migrating-from-ROS1/Migrating-CPP-Packages
+   Migrating-from-ROS1/Migrating-Python-Package-Example
    Migrating-from-ROS1/Migrating-Python-Packages
    Migrating-from-ROS1/Migrating-Launch-Files
    Migrating-from-ROS1/Migrating-Parameters

source/How-To-Guides/Migrating-from-ROS1/Migrating-Python-Package-Example.rst

@@ -0,0 +1,129 @@
+Migrating a Python Package Example
+==================================
+
+.. contents:: Table of Contents
+   :depth: 2
+   :local:
+
+This guide shows how to migrate an example Python package from ROS 1 to ROS 2.
+
+Prerequisites
+-------------
+
+You need a working ROS 2 installation, such as :doc:`ROS {DISTRO} <../../Installation>`.
+
+The ROS 1 code
+--------------
+
+Say you have a ROS 1 package called ``talker_py`` that uses ``rospy`` in one node, called ``talker_py_node``.
+This package is in a catkin workspace, located at ``~/ros1_talker``.
+
+Your ROS 1 workspace has the following directory layout:
+
+.. code-block:: bash
+
+   $ cd ~/ros1_talker
+   $ find .
+   .
+   src
+   src/talker_py
+   src/talker_py/package.xml
+   src/talker_py/CMakeLists.txt
+   src/talker_py/src
+   src/talker_py/src/talker_py
+   src/talker_py/src/talker_py/__init__.py
+   src/talker_py/scripts
+   src/talker_py/scripts/talker_py_node
+   src/talker_py/setup.py
+
+The files have the following content:
+
+``src/talker_py/package.xml``:
+
+.. code-block:: xml
+
+    <?xml version="1.0"?>
+    <?xml-model href="http://download.ros.org/schema/package_format2.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+    <package format="2">
+        <name>talker_py</name>
+        <version>1.0.0</version>
+        <description>The talker_py package</description>
+        <maintainer email="[email protected]">Brian Gerkey</maintainer>
+        <license>BSD</license>
+
+        <buildtool_depend>catkin</buildtool_depend>
+
+        <depend>rospy</depend>
+        <depend>std_msgs</depend>
+    </package>
+
+``src/talker_py/CMakeLists.txt``:
+
+.. code-block:: cmake
+
+    cmake_minimum_required(VERSION 3.0.2)
+    project(talker_py)
+
+    find_package(catkin REQUIRED)
+
+    catkin_python_setup()
+
+    catkin_package()
+
+    catkin_install_python(PROGRAMS
+        scripts/talker_py_node
+        DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
+    )
+
+``src/talker/src/talker_py/__init__.py``:
+
+.. code-block:: python
+
+    import rospy
+    from std_msgs.msg import String
+
+    def main():
+        pub = rospy.Publisher('chatter', String, queue_size=10)
+        rospy.init_node('talker', anonymous=True)
+        rate = rospy.Rate(10) # 10hz
+        while not rospy.is_shutdown():
+            hello_str = "hello world %s" % rospy.get_time()
+            rospy.loginfo(hello_str)
+            pub.publish(hello_str)
+            rate.sleep()
+
+``src/talker_py/scripts/talker_py_node``:
+
+.. code-block:: python
+
+    #!/usr/bin/env python
+
+    import talker_py
+
+    if __name__ == '__main__':
+        talker_py.main()
+
+``src/talker_py/setup.py``:
+
+.. code-block:: python
+
+    from setuptools import setup
+    from catkin_pkg.python_setup import generate_distutils_setup
+
+    setup_args = generate_distutils_setup(
+        packages=['talker_py'],
+        package_dir={'': 'src'}
+    )
+
+    setup(**setup_args)
+
+Migrating to ROS 2
+------------------
+
+TODO
+
+Conclusion
+----------
+
+You have learned how to migrate an example Python ROS 1 package to ROS 2.
+Use the :doc:`Migrating Python Packages reference page <./Migrating-Python-Packages>` to help you migrate your own Python packages from ROS 1 to ROS 2.

source/How-To-Guides/Migrating-from-ROS1/Migrating-Python-Packages.rst

@@ -3,8 +3,8 @@
    Migration-Guide-Python
    The-ROS2-Project/Contributing/Migration-Guide-Python
 
-Migrating Python Packages
-=========================
+Migrating Python Packages Reference
+===================================
 
 .. contents:: Table of Contents
    :depth: 2