is there a way (through xml or python) that if a civ builds something then they are excluded from building another building

example...if you build Stonehenge than you cant build Pyramids.

I think it's possible for buildings of the same building class (CIV4BuildingClassInfos.xml). Not sure about more complicated solutions.

I think it could be done by moding the CvGameUtils.py python file, but I've never modded that file before so I can really give an specifics.