Is there a way to find out what's connected to each port?

[hmillington]

I'd like my program to behave differently depending on what's connected to the ports.

This works:

ballSensorPresent = False
try:
  ballSensor = ColorSensor(Port.A)
  ballSensorPresent = True
  print("Ball sensor detected")
except:
  print("No ball sensor detected")

but I don't suppose trapping exceptions is the best way to do it. I see there's a method for EV3, #152, so maybe something similar works with PU hubs?

[laurensvalk]

Try this example: https://docs.pybricks.com/en/latest/iodevices/pupdevice.html#detecting-devices

[hmillington]

Thank you. So exceptions of one sort or another are the best/only way to do it...

[laurensvalk]

If you know that something is connected but not what, you can use the PUPDevice class without exceptions.

That said, exceptions are quite a conventional coding pattern for this kind of thing.

I can see that in some applications, this can make your main code a bit harder to read. For that use case, you could perhaps define functions to detect devices, and import those functions into your main code.

[laurensvalk]

Here's a variant that could help you keep your main script fairly clean.

Put this in a file called device_handler.py:

from pybricks.iodevices import PUPDevice
from pybricks.parameters import Port
from uerrno import ENODEV

def get_device_id(port):
    """Get device ID, or 0 if nothing is attached."""
    try:
        device = PUPDevice(port)
        return device.info()["id"]
    except OSError as ex:
        if ex.args[0] == ENODEV:
            return 0
        else:
            raise

Then, in your main script, you can do:

from device_handler import get_device_id
from pybricks.parameters import Port

# Get device ID
id = get_device_id(Port.A)
print(id)