OSError when setting too large speed_sp

• ev3dev version: 4.4.68-20-ev3dev-ev3

One of my students ran into an issue where they set motor.run_forever for a large motor via a formula. Once the result reached 1050 they got a OSError: InvalidArgument. 1050 is the max_speed. I think the library should cap the input at 1050 (or the max_speed of the corresponding tacho-motor) or throw a ValueError instead. The error message, in any way, is very cryptic considering how easy it is to trigger.

speed_R was set to something larger than the max_speed.

Traceback (most recent call last):
  File "./braitenberg4b.py", line 26, in <module>
    motor_R.run_forever(speed_sp = speed_R)
  File "/usr/lib/python3/dist-packages/ev3dev/core.py", line 793, in run_forever
    setattr(self, key, kwargs[key])
  File "/usr/lib/python3/dist-packages/ev3dev/core.py", line 583, in speed_sp
    self._speed_sp = self.set_attr_int(self._speed_sp, 'speed_sp', value)
  File "/usr/lib/python3/dist-packages/ev3dev/core.py", line 217, in set_attr_int
    return self._set_attribute(attribute, name, str(int(value)))
  File "/usr/lib/python3/dist-packages/ev3dev/core.py", line 206, in _set_attribute
    attribute.write(value.encode())
OSError: [Errno 22] Invalid argument

[dwalton76]

I’m way behind on ev3dev-Python lately but the proposed idea sounds like a good idea to me

[maweki]

it isn’t an even more generic Exception

Of course it is. In the original implementation it was an Exception which is a superclass of OSError (which I marked as erroneous), which is more generic. The error is obviously a ValueError so the exception should be at least a ValueError if not a subclass. I am happy to see that this is fixed with https://github.com/rhempel/ev3dev-lang-python/commit/b009e9eb1f0f4945b9b9e45f2c2a5491c41776a6

The error message is nice and all, but I was concerned with the correct type of exception.

You can ignore the other comment. I was mistaken there.