如何从ROS实时获取Python中的数据？

Question

I am begginer in ROS and I don't understand how to do "publish" and "subscriber" in Python. I have a file .bag and I play this file with rosbag play "file.bag" .

I get the values of topic with rostopic echo /"topic" or rostopic echo -n 1 /"topic" in a xterm.

However, I can't see this values in real time with python to show in a QT GUI. I have read the tutorial http://wiki.ros.org/rospy/Overview/Publishers%20and%20Subscribers but I don't understand it.

Could I have a example with /odom [nav_msgs/Odometry] or /back_laser/filtered [sensor_msgs/LaserScan]

Answer 1

Take a closer look at the tutorials. Especially http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber%28python%29

cd into youd source folder

and create new package:

catkin_create_pkg playground

cd in that directory

cd playground

create a file listener.py and and add following content:

#!/usr/bin/env python
import rospy
from std_msgs.msg import String
from nav_msgs.msg import Odometry
def callback(data):
    rospy.loginfo(rospy.get_caller_id()+"I heard %s",data)

def listener():
    rospy.init_node('listener', anonymous=True)
    rospy.Subscriber("odom", Odometry, callback)
    rospy.spin()

if __name__ == '__main__':
    listener()

make executable:

chmod +x listener.py

start core:

roscore

new terminal, run listener node:

rosrun playground listener.py

new terminal publis some odometry data:

rostopic pub -r1 /odom nav_msgs/Odometry {}

Now you should see some output on your terminal where your listener was started!catki