Skip to content

gh-149083: Use sentinel for os.path.{ALLOW_MISSING,ALL_BUT_LAST} #149613

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.

Sign up for GitHub

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

Open
JelleZijlstra wants to merge 2 commits into
base: main
Choose a base branch
from
+11 −21
Open

gh-149083: Use sentinel for os.path.{ALLOW_MISSING,ALL_BUT_LAST} #149613

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
20b62f7
gh-149083: Use sentinel for os.path.{ALLOW_MISSING,ALL_BUT_LAST}
JelleZijlstra May 9, 2026
71b5fee
update test
JelleZijlstra May 9, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 2 additions & 2 deletions Doc/library/os.path.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -482,13 +482,13 @@ the :mod:`glob` module.)

.. data:: ALL_BUT_LAST

Special value used for the *strict* argument in :func:`realpath`.
:class:`sentinel` used for the *strict* argument in :func:`realpath`.

.. versionadded:: 3.15

.. data:: ALLOW_MISSING

Special value used for the *strict* argument in :func:`realpath`.
:class:`sentinel` used for the *strict* argument in :func:`realpath`.

.. versionadded:: 3.15

Expand Down
22 changes: 5 additions & 17 deletions Lib/genericpath.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -201,20 +201,8 @@ def _check_arg_types(funcname, *args):
raise TypeError("Can't mix strings and bytes in path components") from None


# Singletons with a true boolean value.

@object.__new__
class ALL_BUT_LAST:
"""Special value for use in realpath()."""
def __repr__(self):
return 'os.path.ALL_BUT_LAST'
def __reduce__(self):
return self.__class__.__name__

@object.__new__
class ALLOW_MISSING:
"""Special value for use in realpath()."""
def __repr__(self):
return 'os.path.ALLOW_MISSING'
def __reduce__(self):
return self.__class__.__name__
# Sentinels.
ALL_BUT_LAST = sentinel('ALL_BUT_LAST')
"""Special value for use in realpath()."""
Copy link
Copy Markdown
Member

@serhiy-storchaka serhiy-storchaka May 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is it used as a docstring of the sentinel? I wonder, how can this be implemented?

Copy link
Copy Markdown
Member Author

@JelleZijlstra JelleZijlstra May 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Sentinels don't actually support docstrings. Putting a string like this is an established way to document a variable and I believe Sphinx supports it.

Copy link
Copy Markdown
Member

@serhiy-storchaka serhiy-storchaka May 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Then they are not needed.

ALLOW_MISSING = sentinel('ALLOW_MISSING')
"""Special value for use in realpath()."""
4 changes: 2 additions & 2 deletions Lib/test/test_genericpath.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -330,8 +330,8 @@ def test_realpath_mode_values(self):
for name in 'ALL_BUT_LAST', 'ALLOW_MISSING':
with self.subTest(name):
mode = getattr(self.pathmodule, name)
self.assertEqual(repr(mode), 'os.path.' + name)
self.assertEqual(str(mode), 'os.path.' + name)
self.assertEqual(repr(mode), name)
self.assertEqual(str(mode), name)
self.assertTrue(mode)
self.assertIs(copy.copy(mode), mode)
self.assertIs(copy.deepcopy(mode), mode)
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-05-09-10-58-34.gh-issue-149083.I53mx4.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
:data:`os.path.ALLOW_MISSING` and :data:`os.path.ALL_BUT_LAST` are now
instances of :class:`sentinel`.
Loading