Hi,
Ok, so you get that message from pylint, not from the Python interpreter when you try to run the code, right?
The thing with PyROOT is that everything is dynamic, there is no TTree Python class that is created beforehand. What happens is that, by interrogating the ROOT C++ interpreter, PyROOT can learn about C++ entities (e.g. classes) at runtime and create Python proxies for them. That must be the reason why you get that message from pylint, since there is no TTree class in the PYTHONPATH, it’s created on the fly.