The supported arguments to from_file and related is str. Passing a pathlib Path results in:
Traceback (most recent call last):
File "[path]/process.py", line 8, in <module>
tape = ENDFtk.tree.Tape.from_file(p)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: from_file(): incompatible function arguments. The following argument types are supported:
1. (filename: str) -> ENDFtk.tree.Tape
Invoked with: PosixPath('[filename]')
Converting to str works just fine. I have no idea if it is possible to make this more user-friendly with the PyBind11 stuff.