Example script with a control logic to move the iRobot Create 2

node.py

#!/usr/bin/env python
import rospy
from ca_msgs.msg import Bumper
from std_msgs.msg import Float32
from geometry_msgs.msg import Twist, Vector3

class MiClase():

  def __init__(self):
    rospy.init_node("node_name", log_level=rospy.INFO)
    self.sub = rospy.Subscriber("bumper", Bumper, self.callback)
    self.pub = rospy.Publisher("/cmd_vel", Twist, queue_size=10)
    self.motor_pub = rospy.Publisher("/main_motor", Float32, queue_size=10)
    rospy.on_shutdown(self.apagar)
    self.apagado = False
    rospy.spin()
  
  def apagar(self):
    self.apagado = True
    self.motor_pub.publish(0.0)
  
  def callback(self, data):
    if not self.apagado:
      rospy.loginfo("{} {}".format(data.is_left_pressed, data.is_right_pressed))
      if data.is_left_pressed:
        self.rotar_der()
      elif data.is_right_pressed:
        self.rotar_izq()
      else:
        self.parar()
      self.motor_pub.publish(0.5)
  
  def rotar_izq(self):
    self.pub.publish(Twist(Vector3(), Vector3(0, 0, 0.1)))
  
  def rotar_der(self):
    self.pub.publish(Twist(Vector3(), Vector3(0, 0, -0.1)))

  def mover(self):
    msg = Twist()
    msg.linear.x = 0
    msg.angular.z = -0.1
    self.pub.publish(msg)
  
  def parar(self):
    linear = Vector3(0, 0 ,0)
    angular = Vector3(0, 0, 0)
    msg = Twist(linear, angular)
    self.pub.publish(msg)

if __name__ == "__main__":
  clase = MiClase()