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1. Eclips4

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   testsTests in the Lib/test dirTests in the Lib/test dir

   OS-windows

   on Oct 31, 2024
2. zooba commented on Oct 31, 2024

   

   zooba

   on Oct 31, 2024

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   What's your exact OS build number? This function will have been affected by more recent Windows updates, though I've never seen this behaviour before.
3. Eclips4 commented on Nov 1, 2024

   

   Eclips4

   on Nov 1, 2024

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   What's your exact OS build number?

   Not that familiar with Windows so not sure what do you mean

   PS C:\Users\eclips4> (Get-ComputerInfo).WindowsBuildLabEx
   26100.1.amd64fre.ge_release.240331-1435
   

   FWIW, this is a Windows 11 which I downloaded two days ago. So, yes, this build should be pretty new.
4. zooba commented on Nov 11, 2024

   

   zooba

   on Nov 11, 2024

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   Okay, so I have the same build and it doesn't repro here, but I noticed that 268435472 = 0x10000010 which is 16 plus an invalid bit. So my guess is that the API underlying the regular stat() call is not filtering out unknown bits and your file system is somehow deciding to return one.

   Not sure what the best approach here would be. There's a FILE_ATTRIBUTE_VALID_FLAGS constant but it changes with our build settings. Masking inside stat would clear out the extra bit, but if it ever became meaningful then we'd need to update Python to see it. We can probably filter the test quite reasonably to mask with 0x0000FFFF first (any actual use of this field should be checking for certain bits, so the extra one isn't an issue), so maybe that's good enough here?
5. vstinner commented on Mar 24, 2026

   

   vstinner

   on Mar 24, 2026

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   I can reproduce the issue on Windows 11 version 24H2 (Windows-11-10.0.26100-SP0 says the platform module) on a NTFS filesystem.

   Example:

   import os
   dirname = "tmpdir"
   os.mkdir(dirname)
   entry = {entry.name: entry for entry in os.scandir()}[dirname]
   st1 = entry.stat()
   st2 = os.stat(dirname)
   os.rmdir(dirname)
   print("os.scandir() stat:", hex(st1.st_file_attributes))
   print("os.stat():", hex(st2.st_file_attributes))

   Output:

   os.scandir() stat: 0x10
   os.stat(): 0x10000010
   

   Or test_os failure:

   C:\victor\python\main>python -m test test_os.test_os -m test_attributes -v
   
   == CPython 3.15.0a7+ (heads/pr/146347-dirty:d0830f8f8f9, Mar 24 2026, 00:56:18) [MSC v.1950 64 bit (AMD64)]
   == Windows-11-10.0.26100-SP0 little-endian
   == Python build: debug
   == cwd: C:\victor\python\main\build\test_python_worker_8096æ
   (...)
   
   FAIL: test_attributes (test.test_os.test_os.TestScandir.test_attributes)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "C:\victor\python\main\Lib\test\test_os\test_os.py", line 4885, in test_attributes
       self.check_entry(entry, 'dir', True, False, False)
       ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "C:\victor\python\main\Lib\test\test_os\test_os.py", line 4853, in check_entry
       self.assert_stat_equal(entry.stat(),
       ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
                              entry_stat,
                              ^^^^^^^^^^^
                              os.name == 'nt' and not is_symlink)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "C:\victor\python\main\Lib\test\test_os\test_os.py", line 4812, in assert_stat_equal
       self.assertEqual(getattr(stat1, attr),
       ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
                        getattr(stat2, attr),
                        ^^^^^^^^^^^^^^^^^^^^^
                        (stat1, stat2, attr))
                        ^^^^^^^^^^^^^^^^^^^^^
   AssertionError: 16 != 268435472 : (os.stat_result(st_mode=16895, st_ino=0, st_dev=0, st_nlink=0, st_uid=0, st_gid=0, st_size=0, st_atime=1774264899, st_mtime=1774264899, st_ctime=1774264899), os.stat_result(st_mode=16895, st_ino=12103423998593687, st_dev=10298252993199238233, st_nlink=1, st_uid=0, st_gid=0, st_size=0, st_atime=1774264899, st_mtime=1774264899, st_ctime=1774264899), 'st_file_attributes')
   
6. vstinner

   changed the title [-]``test_os`` fails on Windows[/-] [+]``test_os.test_attributes()`` fails on Windows[/+] on Mar 24, 2026
7. vstinner commented on Mar 24, 2026

   

   vstinner

   on Mar 24, 2026

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   I found multiple articles saying that 0x10000000 means "directory" in "(DOS) file attribute" of NTFS:

   • http://ftp.kolibrios.org/users/Asper/docs/NTFS/ntfsdoc.html
   • https://wiki.osdev.org/User:Tudoros1/FileSystems/NTFS
   • https://us.mrtlab.com/filesystem/NTFS-standard-two_3.html

   But this constant is not listed in File Attribute Constants documentation.
8. Wanbinyu

   added a commit that references this issue on Sep 16, 2026

   pythongh-126253: Add a Tests NEWS entry

   4fcb07e
9. hugovk

   added a commit that references this issue on Nov 4, 2026

   Merge branch 'main' into pythongh-126253-test-os-file-attributes

   744f998
10. hugovk commented on Nov 4, 2026

    

    hugovk

    on Nov 4, 2026

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    This is now showing up on this tier 1 worker after a reboot:

    • https://buildbot.python.org/#/builders/729/builds/11792 ARM64 Windows
    • https://buildbot.python.org/#/builders/730/builds/14943 ARM64 Windows Non-Debug 3.x

    (cc @zware)

    FAIL: test_attributes (test.test_os.test_os.TestScandir.test_attributes)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "C:\Users\buildworker\buildarea\3.x.ware-win11-arm64\build\Lib\test\test_os\test_os.py", line 5108, in test_attributes
        self.check_entry(entry, 'dir', True, False, False)
        ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "C:\Users\buildworker\buildarea\3.x.ware-win11-arm64\build\Lib\test\test_os\test_os.py", line 5076, in check_entry
        self.assert_stat_equal(entry.stat(),
        ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
                               entry_stat,
                               ^^^^^^^^^^^
                               os.name == 'nt' and not is_symlink)
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "C:\Users\buildworker\buildarea\3.x.ware-win11-arm64\build\Lib\test\test_os\test_os.py", line 5035, in assert_stat_equal
        self.assertEqual(getattr(stat1, attr),
        ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
                         getattr(stat2, attr),
                         ^^^^^^^^^^^^^^^^^^^^^
                         (stat1, stat2, attr))
                         ^^^^^^^^^^^^^^^^^^^^^
    AssertionError: 16 != 268435472 : (os.stat_result(st_mode=16895, st_ino=0, st_dev=0, st_nlink=0, st_uid=0, st_gid=0, st_size=0, st_atime=1793728813, st_mtime=1793728813, st_ctime=1793728813), os.stat_result(st_mode=16895, st_ino=19421773393521866, st_dev=6923181900724247706, st_nlink=1, st_uid=0, st_gid=0, st_size=0, st_atime=1793728813, st_mtime=1793728813, st_ctime=1793728813), 'st_file_attributes')

    There's a pending PR at #156305.

    👀React with 👀2Reacted by Victor Stinner and Zachary Ware