[Tutor] A question about None

[dn]

On 22/08/2021 19.25, Phil wrote:
> 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?


What if the distance is 20(cm)?

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

Assuming:
- correct understanding of >, <, or =
- start() applies in either case and as long as the sensor returned a value
- consider adding a sleep() to the loop, depending upon the necessary
frequency of sensing
-- 
Regards,
=dn