python - Error with simple subclassing of pathlib.Path: no _flavour attribute

Question

I'm trying to sublclass Path from pathlib, but I failed with following error at instantiation

from pathlib import Path
class Pl(Path):
    def __init__(self, *pathsegments: str):
        super().__init__(*pathsegments)

Error at instantiation

AttributeError: type object 'Pl' has no attribute '_flavour'

Update: I'm inheriting from WindowsPath still doesn't work.

TypeError: object.__init__() takes exactly one argument (the instance to initialize)

Answer 1

Part of the problem is that the Path class implements some conditional logic in __new__ that doesn't really lend itself to subclassing. Specifically:

    def __new__(cls, *args, **kwargs):
        if cls is Path:
            cls = WindowsPath if os.name == 'nt' else PosixPath

This sets the type of the object you get back from Path(...) to either PosixPath or WindowsPath, but only if cls is Path, which will never be true for a subclass of Path.

That means within the __new__ function, cls won't have the_flavourattribute (which is set explicitly for the*WindowsPath and *PosixPath classes), because your Pl class doesn't have a _flavour attribute.

I think you would be better off explicitly subclassing one of the other classes, such as PosixPath or WindowsPath.