Hello @jfcaron ,
Since ROOT 6.22 we have a new PyROOT and we are also writing new documentation.
Part of it is the manual, which you already referenced.
The other piece of documentation we are writing is the pythonization docs, e.g. how to use ROOT C++ classes from Python. For example, related to your question, you have the TTree pythonization docs here (see PyROOT box):
which explain what’s different when you use
Branch from Python.
That being said, the new way to process TTrees in ROOT that we are promoting is called
You can read existing datasets, transform them and obtain results, or create/extend datasets and write them back to ROOT files. We’d be happy to help you with it if you decide to use it instead of the more low-level TTree interface.