1.关于无rospy.spin()调用多次callback 2. subscrib后面语句和callback函数运行顺序

#!/usr/bin/env python
import rospy
from bzrobot_msgs.msg import bzr_WheelLinearVels

#from threading import Thread
from time import sleep

class RS232MotorComm():

    def callback(self, data):
        print ‘****************************************start callback‘
        self.flg=0
        sleep(0.05)
        rospy.loginfo("speed %f %f",data.leftWheelLinearVel, data.rightWheelLinearVel)
        self.flg=1
    
    def motor_listener(self):
        self.flg=1
        rospy.init_node(‘rs232_motor_comm‘, anonymous=True)

        rospy.Subscriber("control_wheel_linear_vel", bzr_WheelLinearVels, self.callback)
        #sleep(1)
    
        r = rospy.Rate(10) # 10hz
        while self.flg==1:#not rospy.is_shutdown():#True:
            print‘where‘
            r.sleep()  #time must enough for callback,or it will out while loop
            print‘after sleep 1s‘

if __name__ == ‘__main__‘:
    
    motor_controller = RS232MotorComm()
    print‘the1‘

    motor_controller.motor_listener()
    #rospy.spin()
    print‘end‘