rosrun turtlesim    turtlesim_node
rosrun turtlesim turtle_teleop_key

rqt_graph

rostopic info /turtle1/cmd_vel

rosmsg show geometry_msgs/Twist

geometry_msgs/Vector3 linear
  float64 x
  float64 y
  float64 z
geometry_msgs/Vector3 angular
  float64 x
  float64 y
  float64 z

rostopic pub /turtle1/cmd_ geometry_msgs/Twist "linear:
  x: 0.0
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0

import rospy
from geometry_msgs.msg import Twist
rospy.init_node("twist_pub")
pub=rospy.Publisher("/turtle1/cmd_vel",Twist,
queue_size=10)
rate=rospy.Rate(10)
twist=Twist()
twist.linear.x=1
twist.angular.z=1
while not rospy.is_shutdown():
    pub.publish(twist)
    rate.sleep()

rostopic list

rostopic echo /turtle1/pose

rostopic info /turtle1/pose 

rosmsg show turtlesim/Pose

float32 x
float32 y
float32 theta
float32 linear_velocity
float32 angular_velocity

import rospy
from turtlesim.msg import Pose
def doMsg(msg):
    rate.sleep()
    rospy.loginfo("乌龟x:%fm乌龟y:%f,乌龟角度:%f,乌龟线速度：%f,乌龟角速度:%f",msg.x,msg.y,msg.theta,msg.linear_velocity,msg.angular_velocity)
rospy.init_node("sub_turtle")
sub=rospy.Subscriber("turtle1/pose",Pose,
queue_size=10,callback=doMsg)
rate=rospy.Rate(1)
rospy.spin()

rosservice list

rosservice type /spawn

rossrv show turtlesim/Spawn

float32 x
float32 y
float32 theta
string name
---
string name

rosservice call /spawn "x: 0.0 
y: 4.0
theta: 0.0
name: 'dsa'" 
name: "dsa"

import rospy
from turtlesim.srv import *
rospy.init_node("tospawn")
client=rospy.ServiceProxy("/spawn",Spawn)
request=SpawnRequest()
request.x=5
request.y=4
request.theta=50
request.name="dfg"
#client.wait_for_service()
rospy.wait_for_service("spawn")
try:
    response=client.call(request)
    rospy.loginfo("乌龟的名字%s",response.name)
except:
    rospy.loginfo("异常")