[Tutor] A question about None

[Phil]

The distance sensor outputs "None" if the distance is greater than can 
be measured and "None", of course cannot be compared. So I came up with 
the following which is not quite correct:

while True
     if distance_sensor.get_distance_cm() is not None:
         if distance_sensor.get_distance_cm() > 20:
             motor_pair.set_default_speed(20)
             motor_pair.start()
         else:
             continue

     elif distance_sensor.get_distance_cm() is not None:
         if distance_sensor.get_distance_cm() < 20:
             motor_pair.set_default_speed(-20)
             motor_pair.start()
         else:
             continue

The idea is that if "None" returned from the sensor then nothing will 
happen and the loop will continue until "None" is not returned. Can 
anyone see the error of my ways?

-- 
Regards,
Phil