On Wed, Feb 9, 2022 at 11:59 AM Barney Gale <barney.g...@gmail.com> wrote:
> Penny for your thoughts on those questions, Brett? Protocols are new to > me. I see importlib.abc.Traversable is a Protocol, and I'm giving PEP 544 a > read now. > Protocols would let folks rely on a common Path object API w/o having to require the object come from pathlib itself or explicitly subclass something (which I admit would be rare, but there's no reason to artificially constrain this either). Now maybe this is too broad of an API for people to care, but since protocols are also ABCs it doesn't inherently make things worse, either. So I would say subclassing Protocol makes sense while still using abc.abstractmethod for methods people must implement. > > I reckon only stat(), open() and iterdir() would be essential for users to > implement. > Seems like a reasonable set to have to implement. -Brett > > On Wed, 9 Feb 2022 at 19:02, Brett Cannon <br...@python.org> wrote: > >> One thing to discuss (and which has been brought up on the PR), is >> whether this should be an ABC to force people to explicitly raise >> `NotImplementedError`? >> >> The next question is whether any of this should be a (very wide) protocol >> instead of an ABC? >> >> On Wed, Feb 9, 2022 at 7:05 AM Barney Gale <barney.g...@gmail.com> wrote: >> >>> Over the last couple of years I've been tidying up the pathlib >>> internals, with a view towards adding an AbstractPath class to the >>> hierarchy. Users would be able to subclass AbstractPath to implement other >>> kinds of filesystems: s3, google cloud storage, pandas, ftp, git, zip and >>> tar files, etc. By implementing some abstract methods (stat(), iterdir(), >>> open(), etc) they'd benefit from a number of derived methods (is_dir(), >>> glob(), read_text(), etc). There's already a healthy ecosystem of PyPI >>> packages attempting this, but there's presently no officially-supported >>> route. >>> >>> I've now submitted a PR that adds an initial underscore-prefixed >>> implementation of this class: >>> https://github.com/python/cpython/pull/31085. The implementation is >>> simple: wherever Path calls functions in os, io, pwd, etc, AbstractPath >>> instead raises NotImplementedError. The Path class becomes an >>> implementation of AbstractPath. >>> >>> These methods directly raise NotImplementedError: cwd(), stat(), >>> iterdir(), readlink(), resolve(), expanduser(), owner(), group(), open(), >>> touch(), mkdir(), symlink_to(), hardlink_to(), rename(), replace(), >>> chmod(), unlink(), rmdir() >>> >>> These methods call through to the above methods: absolute(), lstat(), >>> exists(), is_dir(), is_file(), is_mount(), is_symlink(), is_block_device(), >>> is_char_device(), is_fifo(), is_socket(), home(), samefile(), scandir(), >>> glob(), rglob(), read_bytes(), read_text(), write_bytes(), write_text(), >>> lchmod(), link_to() >>> >>> Some methods aren't applicable to some kinds of filesystems, e.g. zip >>> files don't support symlinks, working directories or home directories. In >>> these cases I think it's reasonable to raise NotImplementedError. Indeed, >>> pathlib.Path methods already raise NotImplementedError when certain local >>> filesystem features aren't available (readlink(), group(), etc). >>> >>> If any readers of this list have previously tried to extend pathlib to >>> other domains, or are otherwise interested in pathlib development, please >>> could you let me know what you think of the proposed API? >>> >>> Many thanks >>> _______________________________________________ >>> Python-Dev mailing list -- python-dev@python.org >>> To unsubscribe send an email to python-dev-le...@python.org >>> https://mail.python.org/mailman3/lists/python-dev.python.org/ >>> Message archived at >>> https://mail.python.org/archives/list/python-dev@python.org/message/JB7QGDNI2CNXFX7LQQ2X2WPOZ7DWVNQL/ >>> Code of Conduct: http://python.org/psf/codeofconduct/ >>> >>
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