Python implements Hello world.
Writing Python programs in ROS is similar to writing C++ programs.
step1. Create a workspace
Ctrl+Alt+T to open the terminal and enter: [Create a workspace in the main directory]
mkdir -p helloworld_ws/src
cd helloworld_ws
catkin_make
Among them, helloworld_ws is the name of the workspace we named, and catkin_make is a compilation command, which will help us create the files we need and output several logs. The successful results are as follows:
step2. Create a function package
Continue to enter in the terminal: [Create a function package in the src file of the workspace]
cd src
catkin_create_pkg helloworld roscpp rospy std_msgs
Among them, helloworld is the name of our function package, roscpp, rospy and std_msgs are the added dependencies. These dependencies are some of the most basic dependencies for us to run programs in ROS. The successful results are as follows: [The message dependency in the lower version of ROS may be ros_msgs]
step3. Edit the source file
Create a new folder named [scripts] in the function package at the same level as the [src] folder
Enter in the terminal: [Create source file]
cd ~/helloworld_ws/src/helloworld/scripts
gedit talker.py
Enter in the blank document: 【Hello world!】
#!/home/lg/anaconda3/bin/python
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
gedit listener.py
#!/home/lg/anaconda3/bin/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
# name 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()
step4. Edit the configuration file
Open the CMakeLists.txt in the helloworld function package [helloworld_ws/src/helloword/CMakeLists.txt]
catkin_install_python(PROGRAMS
scripts/talker.py
scripts/listener.py
DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
)
step5. Compile and execute and open
a new input: [Start ros core]
roscore
Re-open a terminal and enter: [compile and execute in the workspace]
cd ~/helloworld_ws
catkin_make
source ./devel/setup.bash
rosrun helloworld talker.py
Re-open a terminal and enter: [compile and execute in the workspace]
cd ~/helloworld_ws
catkin_make
source ./devel/setup.bash
rosrun helloworld listener.py
