It is also explained here that writing ROS function packages in Python also requires CMakelists.txt

Retrieved from: https://blog.csdn.net/u013832707/article/details/53980759

Implement ROS node with Python

Lasting determination 2017-01-02 18:28:59 21390 Collection 24

Category column: ROS Python Article tags: python ROS

The main programming language of ROS is not only C++, but also Python. Here is an explanation of how to use Python to write ROS nodes. For tutorials, refer to the official website rospy_tutorials .

1. Write a simple publisher and subscriber

1Create a workspace

Create a folder hello_rospy, then create a subdirectory src in this directory, cd to the src directory, and run the following command to create a work package

catkin_create_pkg beginner_tutorials std_msgs rospy roscpp

cd to the upper directory of src, compile and source

cd ..
catkin_make
. devel/setup.bash

2 write publisher program and subscriber program

roscd beginner_tutorials/ 
mkdir scripts
cd scripts

Create a new talker.py file in the scripts directory and fill in the following content:

#!/usr/bin/env python
# license removed for brevity
import rospy
from std_msgs.msg import String
 
def talker():
     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()
 
 if __name__ == '__main__':
     try:
         talker()
     except rospy.ROSInterruptException:
         pass

Create a new listener.py file in the scripts directory and fill in the following content:

#!/usr/bin/env python
import rospy
from std_msgs.msg import String
 
def callback(data):
    rospy.loginfo(rospy.get_caller_id() + "I heard %s", data.data)
     
def listener():
 
    # In ROS, nodes are uniquely named. If two nodes with the same
    # node are launched, the previous one is kicked off. The
    # anonymous=True flag means that rospy will choose a unique
    # name for our 'listener' node so that multiple listeners can
    # run simultaneously.
    rospy.init_node('listener', anonymous=True)
 
    rospy.Subscriber("chatter", String, callback)
 
    # spin() simply keeps python from exiting until this node is stopped
    rospy.spin()
 
if __name__ == '__main__':
    listener()

Remember to change the permissions to executable files

3. Compile

Modify Cmakelist.txt as follows:

cmake_minimum_required(VERSION 2.8.3)
project(beginner_tutorials)

## 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
  roscpp
  rospy
  std_msgs
)

catkin_package()

Just run it directly in the workspace catkin_make.

4. Run

Execute the following commands in the 3 terminals respectively

roscore

rosrun beginner_tutorials talker.py

rosrun beginner_tutorials listener.py

The results are as follows:
Write picture description here

Use Python to implement ROS nodes (this also explains that writing ROS function packages in Python also requires CMakelists.txt)