how can i measurement object distance between -180 and 180 degree. I cant adjust ranges value.

    import rospy
from sensor_msgs.msg import LaserScan


class LazerVerisi():
    def  __init__(self):
        rospy.init_node("laser")
        rospy.Subscriber("scan",LaserScan,self.laserCB)
        rospy.spin()

    def laserCB(self,msg):
        front = list(msg.ranges[0:360])