If I understand correctly, your task is to find the support loads of the columns. The wall supports should be suppressed.
I suggest two possible methods:
a) Using the normal force of the beams may be easier to filter.
b) Another possibility is to find the support nodes using the start/end nodes of the SLNs. I would do this outside python and use the node numbers later in the python code (especially if it is urgent and I only have to work with one model), but it should be possible inside python too.
Regards
gmay