08b-ROSPY_Building.md

Setting up the catkin package to build ROSPY

For basic ROSPY usage, we do not need to build ROSPY into our Catkin Package.
Simply importing the rospy library into Python is sufficient for basic usage.

For more advanced ROSPY usage, it is advised to have a proper setup in your Catkin Package to build and compile your python code with any libraries, messages, services, and resources you may have in your package.

Prequisites

This section requires the catkin_ws to be initialized and the turtlebot_dabit package created.
Please click here to learn how to initialize the catkin workspace

Catkin Package Setup

For this tutorial, we will be using the turtlebot_dabit catkin package we created. In order to enable building ROSPY files in our package, we need to edit the CMakeLists.txt and package.xml to build with our dependencies.

1. Source your catkin workspace and cd to the turtlebot_dabit package:

   1. cd ~/catkin_ws/src/turtlebot_dabit

2. Edit your package.xml and add build and run dependencies:

   1. gedit package.xml

      • Near the bottom of the file, find the <buildtool_depend>catkin</buildtool_depend> line:

        ...
        <buildtool_depend>catkin</buildtool_depend>
        ...

      • Add the build_depend and run_depend tags for roscpp underneath the buildtool_depend line:

        <build_depend>rospy</build_depend>
        <run_depend>rospy</run_depend>

      • The resulting package.xml

        <?xml version="1.0"?>
        <package>
          <name>turtlebot_dabit</name>
          <version>0.0.0</version>
          <description>The turtlebot_dabit package</description>
        
          <!-- One maintainer tag required, multiple allowed, one person per tag -->
          <!-- Example:  -->
          <!-- <maintainer email="jane.doe@example.com">Jane Doe</maintainer> -->
          <maintainer email="user@todo.todo">user</maintainer>
        
        
          <!-- One license tag required, multiple allowed, one license per tag -->
          <!-- Commonly used license strings: -->
          <!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->
          <license>TODO</license>
        
          <!-- ... -->
        
          <buildtool_depend>catkin</buildtool_depend>
          <build_depend>rospy</build_depend>
          <run_depend>rospy</run_depend>
        
          <!-- The export tag contains other, unspecified, tags -->
          <export>
            <!-- Other tools can request additional information be placed here -->
        
          </export>
        </package>

3. Edit your CMakeLists.txt and add your dependencies to it

   1. gedit CMakeLists.txt

      • Near the top of the file, find the find_package(catkin REQUIRED) line:

        ...
        find_package(catkin REQUIRED)
        ...
        

      • Replace that line with:

        find_package(catkin REQUIRED COMPONENTS
          rospy
        )
        

      • Near the top of the file, find the # catkin_python_setup() line:

        ...
        # catkin_python_setup()
        ...
        

      • Uncomment that line:

        catkin_python_setup()
        

      • Near the middle of the file, find the catkin_package( line:

        ...
        catkin_package(
        #  INCLUDE_DIRS include
        #  LIBRARIES turtlebot_dabit
        #  CATKIN_DEPENDS other_catkin_pkg
        #  DEPENDS system_lib
        )
        ...
        

      • Replace that line with:

        catkin_package(
          INCLUDE_DIRS
          CATKIN_DEPENDS rospy
        )
        

      • Near the middle of the file, find the # include_directories(include) line:

        ...
        # include_directories(include)
        ...
        

      • Replace that line with:

        include_directories(
          ${catkin_INCLUDE_DIRS}
        )
        

      • The resulting CMakeLists.txt

        cmake_minimum_required(VERSION 2.8.3)
        project(turtlebot_dabit)
        
        ## Add support for C++11, supported in ROS Kinetic and newer
        # add_definitions(-std=c++11)
        
        ## Find catkin macros and libraries
        ## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
        ## is used, also find other catkin packages
        find_package(catkin REQUIRED COMPONENTS
          rospy
        )
        
        #  ...
        
        ## Uncomment this if the package has a setup.py. This macro ensures
        ## modules and global scripts declared therein get installed
        ## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
        catkin_python_setup()
        
        # ...
        
        ###################################
        ## catkin specific configuration ##
        ###################################
        ## The catkin_package macro generates cmake config files for your package
        ## Declare things to be passed to dependent projects
        ## INCLUDE_DIRS: uncomment this if you package contains header files
        ## LIBRARIES: libraries you create in this project that dependent projects also need
        ## CATKIN_DEPENDS: catkin_packages dependent projects also need
        ## DEPENDS: system dependencies of this project that dependent projects also need
        catkin_package(
          INCLUDE_DIRS
          CATKIN_DEPENDS rospy
        )
        
        ###########
        ## Build ##
        ###########
        ## Specify additional locations of header files
        ## Your package locations should be listed before other locations
        include_directories(
          ${catkin_INCLUDE_DIRS}
        )
        
        ## ...
        

4. Test your new package configuration is correct by running catkin_make:

   • catkin_make --directory ~/catkin_ws --pkg turtlebot_dabit

   • Upon success, you should see:

     -- Configuring done
     -- Generating done
     -- Build files have been written to: /home/user/catkin_ws/build
     ####
     #### Running command: "make -j4 -l4" in "/home/user/catkin_ws/build/turtlebot_dabit"
     ####
     

Writing the first ROSPY Python code

Now we get to write our first Python code to communicate with ROS.

1. Create a new file titled rospy_hello_world.py in your scripts folder

   1. gedit ~/catkin_ws/src/turtlebot_dabit/scriptsrospy_hello_world.py

   2. Start with the following Hello World code in gedit:

      #!/usr/bin/env python2.7
      # Import ROS libraries and messages
      import rospy
      
      # Print "Hello!" to terminal
      print "Hello!"
      
      # Initialize the ROS Node named 'opencv_example', allow multiple nodes to be run with this name
      rospy.init_node('opencv_example', anonymous=True)
      
      # Print "Hello ROS!" to the Terminal and ROSLOG
      rospy.loginfo("Hello ROS!")

   3. Save and exit rospy_hello_world.py

2. Set the permissions of your code file to allow execution:
   1. chmod +x ~/catkin_ws/src/turtlebot_dabit/scripts/rospy_hello_world.py"
3. Run your code using rosrun:
   1. source ~/catkin_ws/devel/setup.sh
   2. rosrun turtlebot_dabit rospy_hello_world.py
      • Upon success, you should see: [ INFO] [1492726164.127098818]: Hello ROS!

Additional Resources

ROSPY Tutorials

Return to the main README page