Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

gh-91317: Document that Path does not collapse initial // #32193

Merged
merged 10 commits into from
Jun 10, 2022
33 changes: 30 additions & 3 deletions Doc/library/pathlib.rst
Original file line number Diff line number Diff line change
Expand Up @@ -133,11 +133,13 @@ we also call *flavours*:
PureWindowsPath('c:/Program Files')

Spurious slashes and single dots are collapsed, but double dots (``'..'``)
are not, since this would change the meaning of a path in the face of
symbolic links::
and leading double slashes (``'//'``) are not, since this would change the
meaning of a path for various reasons (e.g. symbolic links, UNC paths)::

>>> PurePath('foo//bar')
PurePosixPath('foo/bar')
>>> PurePath('//foo/bar')
PurePosixPath('//foo/bar')
>>> PurePath('foo/./bar')
PurePosixPath('foo/bar')
>>> PurePath('foo/../bar')
Expand Down Expand Up @@ -166,13 +168,17 @@ we also call *flavours*:
.. class:: PureWindowsPath(*pathsegments)

A subclass of :class:`PurePath`, this path flavour represents Windows
filesystem paths::
filesystem paths, including `UNC paths`_::

>>> PureWindowsPath('c:/Program Files/')
PureWindowsPath('c:/Program Files')
>>> PureWindowsPath('//server/share/file')
PureWindowsPath('//server/share/file')

*pathsegments* is specified similarly to :class:`PurePath`.

.. _unc paths: https://en.wikipedia.org/wiki/Path_(computing)#UNC

Regardless of the system you're running on, you can instantiate all of
these classes, since they don't provide any operation that does system calls.

Expand Down Expand Up @@ -309,6 +315,27 @@ Pure paths provide the following methods and properties:
>>> PureWindowsPath('//host/share').root
'\\'

If the path starts with more than two successive slashes,
:class:`~pathlib.PurePosixPath` collapses them::

>>> PurePosixPath('//etc').root
'//'
>>> PurePosixPath('///etc').root
'/'
>>> PurePosixPath('////etc').root
'/'

.. note::

This behavior conforms to *The Open Group Base Specifications Issue 6*,
paragraph `4.11 *Pathname Resolution* <xbd_path_resolution>`_:

*"A pathname that begins with two successive slashes may be interpreted in
an implementation-defined manner, although more than two leading slashes
shall be treated as a single slash."*

.. xbd_path_resolution: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_11

.. data:: PurePath.anchor

The concatenation of the drive and root::
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Document that :class:`pathlib.PurePath` does not collapse
initial double slashes because they denote UNC paths.