GH-110109: Add `pathlib._PurePathBase` (#110670)

Add private `pathlib._PurePathBase` class: a private superclass of both `PurePath` and `_PathBase`. Unlike `PurePath`, it does not define any of these special methods: `__fspath__`, `__bytes__`, `__reduce__`, `__hash__`, `__eq__`, `__lt__`, `__le__`, `__gt__`, `__ge__`. Its initializer and path joining methods accept only strings, not os.PathLike objects more broadly.

This is important for supporting *virtual paths*: user subclasses of `_PathBase` that provide access to archive files, FTP servers, etc. In these classes, the above methods should be implemented by users only as appropriate, with due consideration for the hash/equality of any backing objects, such as file objects or sockets.

1 files changed, 3 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Library/2023-10-11-02-34-01.gh-issue-110109.RFCmHs.rst b/Misc/NEWS.d/next/Library/2023-10-11-02-34-01.gh-issue-110109.RFCmHs.rst
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+Add private ``pathlib._PurePathBase`` class: a base class for
+:class:`pathlib.PurePath` that omits certain magic methods. It may be made
+public (along with ``_PathBase``) in future.