C++ ROS Tutorial Chatter

edit

Hello everyone, I'm trying to do this simple tutorial using C++ but for some reason i'm having difficulty with it since no executable files are generated under devel/lib

files:

Publisher:

#include "ros/ros.h"
#include "std_msgs/Int32.h"
#include <iostream>

int main (int argc, char **argv)
{
    ros::init(argc, argv,"demo_topic_publisher"); 
    ros::NodeHandle node_obj;     
    ros::Publisher number_publisher = node_obj.advertise<std_msgs::Int32>("/numbers",10); 
    ros::Rate loop_rate(10);     
    int number_count = 0;     

    while (ros::ok()) 
    {
        std_msgs::Int32 msg;  
        msg.data = number_count;     
        ROS_INFO("%d",msg.data);    
        number_publisher.publish(msg);    
        ros::spinOnce();     
        loop_rate.sleep();     
        ++number_count;
    }

    return 0;    
}

Subscriber:

#include "ros/ros.h"
#include "std_msgs/Int32.h"
#include <iostream>

void number_callback(const std_msgs::Int32::ConstPtr& msg)
{    
    ROS_INFO("Received [%d]",msg->data);    
}

int main(int argc, char **argv)
{    
    ros::init(argc, argv, "demo_topic_subscriber");         
    ros::NodeHandle node_obj;       
    ros::Subscriber number_subscriber = node_obj.subscribe("/numbers", 10, number_callback);            
    ros::spin();            
    return 0;     
}

CMakeList.txt:

cmake_minimum_required(VERSION 2.8.3)
project(book_mr)

find_package(catkin REQUIRED COMPONENTS
  actionlib
  actionlib_msgs
  roscpp
  std_msgs
)

catkin_package()

include_directories(
# include
  ${catkin_INCLUDE_DIRS}
)

include_directories(
include
${catkin_INCLUDE_DIRS}
${Boost_INCLUDE_DIRS}
)  

add_executable(demo_topic_publisher src/demo_topic_publisher.cpp)
add_executable(demo_topic_subscriber src/demo_topic_subscriber.cpp)    

add_dependencies(demo_topic_publisher book_mr_generate_messages_cpp)
add_dependencies(demo_topic_subscriber book_mr_generate_messages_cpp)    

target_link_libraries(demo_topic_publisher ${catkin_LIBRARIES})
target_link_libraries(demo_topic_subscriber ${catkin_LIBRARIES})

update 1:

When I use this command to properly initialise the workspace:

    $ catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3

This error comes up:

(base) banana@Science:~/catkin_ws$ catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3
Base path: /home/banana/catkin_ws
Source space: /home/banana/catkin_ws/src
Build space: /home/banana/catkin_ws/build
Devel space: /home/banana/catkin_ws/devel
Install space: /home/banana/catkin_ws/install
####
#### Running command: "cmake /home/banana/catkin_ws/src -DPYTHON_EXECUTABLE=/usr/bin/python3 -DCATKIN_DEVEL_PREFIX=/home/banana/catkin_ws/devel -DCMAKE_INSTALL_PREFIX=/home/banana/catkin_ws/install -G Unix Makefiles" in "/home/banana/catkin_ws/build"
####
-- Using CATKIN_DEVEL_PREFIX: /home/banana/catkin_ws/devel
-- Using CMAKE_PREFIX_PATH: /home/banana/catkin_ws/devel;/opt/ros/melodic
-- This workspace overlays: /home/banana/catkin_ws/devel;/opt/ros/melodic
-- Found PythonInterp: /usr/bin/python3 (found suitable version "3.6.9", minimum required is "2") 
-- Using PYTHON_EXECUTABLE: /usr/bin/python3
-- Using Debian Python package layout
-- Using empy: /usr/bin/empy
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/banana/catkin_ws/build/test_results
-- Found gtest sources under '/usr/src/googletest': gtests will be built
-- Found gmock sources under '/usr/src/googletest': gmock will be built
-- Found PythonInterp: /usr/bin/python3 (found version "3.6.9") 
-- Using Python nosetests: /usr/bin/nosetests-2.7
ImportError: "from catkin_pkg.package import parse_package" failed: No module named 'catkin_pkg'
Make sure that you have installed "catkin_pkg", it is up to date and on the PYTHONPATH.
CMake Error at /opt/ros/melodic/share/catkin/cmake/safe_execute_process.cmake:11 (message):
  execute_process(/usr/bin/python3
  "/opt/ros/melodic/share/catkin/cmake/parse_package_xml.py"
  "/opt/ros/melodic/share/catkin/cmake/../package.xml"
  "/home/banana/catkin_ws/build/catkin/catkin_generated/version/package.cmake")
  returned error code 1
Call Stack (most recent call first):
  /opt/ros/melodic/share/catkin/cmake/catkin_package_xml.cmake:74 (safe_execute_process)
  /opt/ros/melodic/share/catkin/cmake/all.cmake:168 (_catkin_package_xml)
  /opt/ros/melodic/share/catkin/cmake/catkinConfig.cmake:20 (include)
  CMakeLists.txt:56 (find_package)


-- Configuring incomplete, errors ...