Jan 31, 2021 ROS Day 2

pub.py

#!/usr/bin/env python
import rospy 
from geometry_msgs.msg import Twist
import time

# Noted
# Topic: /turtle1/cmd_vel
# Type: geometry_msgs/Twist

def main ():
    rospy.init_node('turtle_commander', anonymous=True)
    rate = rospy.Rate(10) # 10 Hz
    pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
    timestart = time.time() # Get current time in ms
    while not rospy.is_shutdown():
        # TODO
        time_sec = time.time() - timestart # time counting in second
        vel_data = Twist()     # New variable
        print (time_sec)
        if (time_sec <= 2):
            vel_data.angular.z = 1
        else:
            vel_data.angular.z = 0
        pub.publish(vel_data)
        # END
        rate.sleep()
        
if __name__ == '__main__':
    try:
        main()
    except rospy.ROSInterruptException:
        pass