This was an easy fix. The following answer may be only interesting for beginners:

1. Two objects must be created: A daylight control object and a reference point object. The reference point object needs to be hooked to the daylight control object.
2. Afterwards, we can make an output variable: Daylighting Reference Point Illuminance.

---> Be careful: x is not a placeholder for the reference point name but for the reference point number in the daylight control object.

1. After running the simulation, the output was displayed in the rdd file and was accessible from my python script.

I hope that this can save you some time.

Best Regards, P