from gpiozero import Robot, Motor, DistanceSensor
from signal import pause

sensor = DistanceSensor(23, 24, max_distance=1, threshold_distance=0.2)
robot = Robot(left=Motor(4, 14), right=Motor(17, 18))

sensor.when_in_range = robot.backward
sensor.when_out_of_range = robot.stop
pause()