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barneygalejonfoster
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kulikjak
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pythonGH-44626, pythonGH-105476: Fix ntpath.isabs() handling of part-absolute paths (python#113829)
On Windows, `os.path.isabs()` now returns `False` when given a path that starts with exactly one (back)slash. This is more compatible with other functions in `os.path`, and with Microsoft's own documentation. Also adjust `pathlib.PureWindowsPath.is_absolute()` to call `ntpath.isabs()`, which corrects its handling of partial UNC/device paths like `//foo`. Co-authored-by: Jon Foster <jon@jon-foster.co.uk>
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Lines changed: 51 additions & 33 deletions

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‎Doc/library/os.path.rst‎

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@@ -239,12 +239,16 @@ the :mod:`glob` module.)
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.. function:: isabs(path)
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Return ``True`` if *path* is an absolute pathname. On Unix, that means it
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begins with a slash, on Windows that it begins with a (back)slash after chopping
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off a potential drive letter.
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begins with a slash, on Windows that it begins with two (back)slashes, or a
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drive letter, colon, and (back)slash together.
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.. versionchanged:: 3.6
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Accepts a :term:`path-like object`.
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.. versionchanged:: 3.13
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On Windows, returns ``False`` if the given path starts with exactly one
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(back)slash.
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.. function:: isfile(path)
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‎Doc/whatsnew/3.13.rst‎

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@@ -307,6 +307,13 @@ os
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:c:func:`!posix_spawn_file_actions_addclosefrom_np`.
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(Contributed by Jakub Kulik in :gh:`113117`.)
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os.path
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-------
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* On Windows, :func:`os.path.isabs` no longer considers paths starting with
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exactly one (back)slash to be absolute.
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(Contributed by Barney Gale and Jon Foster in :gh:`44626`.)
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pathlib
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-------
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‎Lib/ntpath.py‎

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@@ -77,29 +77,22 @@ def normcase(s):
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return s.replace('/', '\\').lower()
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# Return whether a path is absolute.
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# Trivial in Posix, harder on Windows.
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# For Windows it is absolute if it starts with a slash or backslash (current
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# volume), or if a pathname after the volume-letter-and-colon or UNC-resource
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# starts with a slash or backslash.
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def isabs(s):
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"""Test whether a path is absolute"""
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s = os.fspath(s)
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if isinstance(s, bytes):
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sep = b'\\'
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altsep = b'/'
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colon_sep = b':\\'
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double_sep = b'\\\\'
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else:
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sep = '\\'
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altsep = '/'
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colon_sep = ':\\'
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double_sep = '\\\\'
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s = s[:3].replace(altsep, sep)
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# Absolute: UNC, device, and paths with a drive and root.
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# LEGACY BUG: isabs("/x") should be false since the path has no drive.
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if s.startswith(sep) or s.startswith(colon_sep, 1):
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return True
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return False
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return s.startswith(colon_sep, 1) or s.startswith(double_sep)
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# Join two (or more) paths.

‎Lib/pathlib/_abc.py‎

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Original file line numberDiff line numberDiff line change
@@ -1,5 +1,4 @@
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import functools
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import ntpath
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import posixpath
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from errno import ENOENT, ENOTDIR, EBADF, ELOOP, EINVAL
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from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
@@ -373,10 +372,7 @@ def parents(self):
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def is_absolute(self):
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"""True if the path is absolute (has both a root and, if applicable,
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a drive)."""
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if self.pathmod is ntpath:
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# ntpath.isabs() is defective - see GH-44626.
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return bool(self.drive and self.root)
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elif self.pathmod is posixpath:
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if self.pathmod is posixpath:
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# Optimization: work with raw paths on POSIX.
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for path in self._raw_paths:
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if path.startswith('/'):

‎Lib/test/test_ntpath.py‎

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Original file line numberDiff line numberDiff line change
@@ -227,10 +227,18 @@ def test_split(self):
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tester('ntpath.split("//conky/mountpoint/")', ('//conky/mountpoint/', ''))
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def test_isabs(self):
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tester('ntpath.isabs("foo\\bar")', 0)
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tester('ntpath.isabs("foo/bar")', 0)
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tester('ntpath.isabs("c:\\")', 1)
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tester('ntpath.isabs("c:\\foo\\bar")', 1)
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tester('ntpath.isabs("c:/foo/bar")', 1)
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tester('ntpath.isabs("\\\\conky\\mountpoint\\")', 1)
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tester('ntpath.isabs("\\foo")', 1)
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tester('ntpath.isabs("\\foo\\bar")', 1)
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# gh-44626: paths with only a drive or root are not absolute.
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tester('ntpath.isabs("\\foo\\bar")', 0)
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tester('ntpath.isabs("/foo/bar")', 0)
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tester('ntpath.isabs("c:foo\\bar")', 0)
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tester('ntpath.isabs("c:foo/bar")', 0)
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# gh-96290: normal UNC paths and device paths without trailing backslashes
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tester('ntpath.isabs("\\\\conky\\mountpoint")', 1)

‎Lib/test/test_pathlib/test_pathlib.py‎

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@@ -1011,10 +1011,14 @@ def test_is_absolute(self):
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self.assertTrue(P('c:/a').is_absolute())
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self.assertTrue(P('c:/a/b/').is_absolute())
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# UNC paths are absolute by definition.
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self.assertTrue(P('//').is_absolute())
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self.assertTrue(P('//a').is_absolute())
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self.assertTrue(P('//a/b').is_absolute())
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self.assertTrue(P('//a/b/').is_absolute())
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self.assertTrue(P('//a/b/c').is_absolute())
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self.assertTrue(P('//a/b/c/d').is_absolute())
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self.assertTrue(P('//?/UNC/').is_absolute())
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self.assertTrue(P('//?/UNC/spam').is_absolute())
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def test_join(self):
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P = self.cls

‎Lib/test/test_unittest/test_program.py‎

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@@ -459,8 +459,8 @@ def _join(name):
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def testParseArgsAbsolutePathsThatCannotBeConverted(self):
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program = self.program
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# even on Windows '/...' is considered absolute by os.path.abspath
463-
argv = ['progname', '/foo/bar/baz.py', '/green/red.py']
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drive = os.path.splitdrive(os.getcwd())[0]
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argv = ['progname', f'{drive}/foo/bar/baz.py', f'{drive}/green/red.py']
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self._patch_isfile(argv)
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program.createTests = lambda: None

‎Lib/test/test_zoneinfo/test_zoneinfo.py‎

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@@ -36,6 +36,7 @@
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TEMP_DIR = None
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DATA_DIR = pathlib.Path(__file__).parent / "data"
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ZONEINFO_JSON = DATA_DIR / "zoneinfo_data.json"
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DRIVE = os.path.splitdrive('x:')[0]
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# Useful constants
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ZERO = timedelta(0)
@@ -1679,8 +1680,8 @@ def test_env_variable(self):
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"""Tests that the environment variable works with reset_tzpath."""
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new_paths = [
16811682
("", []),
1682-
("/etc/zoneinfo", ["/etc/zoneinfo"]),
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(f"/a/b/c{os.pathsep}/d/e/f", ["/a/b/c", "/d/e/f"]),
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(f"{DRIVE}/etc/zoneinfo", [f"{DRIVE}/etc/zoneinfo"]),
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(f"{DRIVE}/a/b/c{os.pathsep}{DRIVE}/d/e/f", [f"{DRIVE}/a/b/c", f"{DRIVE}/d/e/f"]),
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]
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for new_path_var, expected_result in new_paths:
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test_cases = [
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[("path/to/somewhere",), ()],
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[
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("/usr/share/zoneinfo", "path/to/somewhere",),
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("/usr/share/zoneinfo",),
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(f"{DRIVE}/usr/share/zoneinfo", "path/to/somewhere",),
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(f"{DRIVE}/usr/share/zoneinfo",),
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],
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[("../relative/path",), ()],
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[
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("/usr/share/zoneinfo", "../relative/path",),
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("/usr/share/zoneinfo",),
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(f"{DRIVE}/usr/share/zoneinfo", "../relative/path",),
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(f"{DRIVE}/usr/share/zoneinfo",),
17041705
],
17051706
[("path/to/somewhere", "../relative/path",), ()],
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[
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(
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"/usr/share/zoneinfo",
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f"{DRIVE}/usr/share/zoneinfo",
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"path/to/somewhere",
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"../relative/path",
17111712
),
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("/usr/share/zoneinfo",),
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(f"{DRIVE}/usr/share/zoneinfo",),
17131714
],
17141715
]
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@@ -1727,9 +1728,9 @@ def test_env_variable_relative_paths(self):
17271728
self.assertSequenceEqual(tzpath, expected_paths)
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17291730
def test_reset_tzpath_kwarg(self):
1730-
self.module.reset_tzpath(to=["/a/b/c"])
1731+
self.module.reset_tzpath(to=[f"{DRIVE}/a/b/c"])
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1732-
self.assertSequenceEqual(self.module.TZPATH, ("/a/b/c",))
1733+
self.assertSequenceEqual(self.module.TZPATH, (f"{DRIVE}/a/b/c",))
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17341735
def test_reset_tzpath_relative_paths(self):
17351736
bad_values = [
@@ -1758,8 +1759,8 @@ def test_tzpath_type_error(self):
17581759
self.module.reset_tzpath(bad_value)
17591760

17601761
def test_tzpath_attribute(self):
1761-
tzpath_0 = ["/one", "/two"]
1762-
tzpath_1 = ["/three"]
1762+
tzpath_0 = [f"{DRIVE}/one", f"{DRIVE}/two"]
1763+
tzpath_1 = [f"{DRIVE}/three"]
17631764

17641765
with self.tzpath_context(tzpath_0):
17651766
query_0 = self.module.TZPATH

‎Misc/NEWS.d/next/Tests/2024-01-08-21-15-48.gh-issue-44626.DRq-PR.rst‎

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@@ -0,0 +1,5 @@
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Fix :func:`os.path.isabs` incorrectly returning ``True`` when given a path
2+
that starts with exactly one (back)slash on Windows.
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Fix :meth:`pathlib.PureWindowsPath.is_absolute` incorrectly returning
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``False`` for some paths beginning with two (back)slashes.

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