用python写一个ros18.04小乌龟走矩形

以下是Python代码：

#!/usr/bin/env python

import rospy
from geometry_msgs.msg import Twist

def move_turtle(lin_vel, ang_vel, distance):
    rospy.init_node('move_turtle', anonymous=True)
    pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
    rate = rospy.Rate(10) # 10hz
    twist = Twist()
    twist.linear.x = lin_vel
    twist.angular.z = ang_vel
    time = distance / lin_vel
    start_time = rospy.Time.now().to_sec()
    while not rospy.is_shutdown():
        pub.publish(twist)
        elapsed_time = rospy.Time.now().to_sec() - start_time
        if elapsed_time > time:
            twist.linear.x = 0
            twist.angular.z = 0
            pub.publish(twist)
            break
        rate.sleep()

if __name__ == '__main__':
    move_turtle(1, 0, 2) # move forward 2m
    rospy.sleep(1) # pause for 1 second
    move_turtle(0, 1, 2) # turn left
    rospy.sleep(1)
    move_turtle(1, 0, 2)
    rospy.sleep(1)
    move_turtle(0, 1, 2)
    rospy.sleep(1)
    rospy.spin()

这个程序会使小乌龟走一个矩形，其中包括向前移动2米、向左转、向前移动2米、向左转、再向前移动2米。您可以根据需要更改移动速度和距离。