Chris Angelico <ros...@gmail.com> writes: > On Sat, Jun 28, 2014 at 11:05 PM, Akira Li <4kir4...@gmail.com> wrote: >> Have you considered adding support for paths relative to directory >> descriptors [1] via keyword only dir_fd=None parameter if it may lead to >> more efficient implementations on some platforms? >> >> [1]: https://docs.python.org/3.4/library/os.html#dir-fd > > Potentially more efficient and also potentially safer (see 'man > openat')... but an enhancement that can wait, if necessary. >
Introducing the feature later creates unnecessary incompatibilities. Either it should be explicitly rejected in the PEP 471 and something-like `os.scandir(os.open(relative_path, dir_fd=fd))` recommended instead (assuming `os.scandir in os.supports_fd` like `os.listdir()`). At C level it could be implemented using fdopendir/openat or scandirat. Here's the function description using Argument Clinic DSL: /*[clinic input] os.scandir path : path_t(allow_fd=True, nullable=True) = '.' *path* can be specified as either str or bytes. On some platforms, *path* may also be specified as an open file descriptor; the file descriptor must refer to a directory. If this functionality is unavailable, using it raises NotImplementedError. * dir_fd : dir_fd = None If not None, it should be a file descriptor open to a directory, and *path* should be a relative string; path will then be relative to that directory. if *dir_fd* is unavailable, using it raises NotImplementedError. Yield a DirEntry object for each file and directory in *path*. Just like os.listdir, the '.' and '..' pseudo-directories are skipped, and the entries are yielded in system-dependent order. {parameters} It's an error to use *dir_fd* when specifying *path* as an open file descriptor. [clinic start generated code]*/ And corresponding tests (from test_posix:PosixTester), to show the compatibility with os.listdir argument parsing in detail: def test_scandir_default(self): # When scandir is called without argument, # it's the same as scandir(os.curdir). self.assertIn(support.TESTFN, [e.name for e in posix.scandir()]) def _test_scandir(self, curdir): filenames = sorted(e.name for e in posix.scandir(curdir)) self.assertIn(support.TESTFN, filenames) #NOTE: assume listdir, scandir accept the same types on the platform self.assertEqual(sorted(posix.listdir(curdir)), filenames) def test_scandir(self): self._test_scandir(os.curdir) def test_scandir_none(self): # it's the same as scandir(os.curdir). self._test_scandir(None) def test_scandir_bytes(self): # When scandir is called with a bytes object, # the returned entries names are still of type str. # Call `os.fsencode(entry.name)` to get bytes self.assertIn('a', {'a'}) self.assertNotIn(b'a', {'a'}) self._test_scandir(b'.') @unittest.skipUnless(posix.scandir in os.supports_fd, "test needs fd support for posix.scandir()") def test_scandir_fd_minus_one(self): # it's the same as scandir(os.curdir). self._test_scandir(-1) def test_scandir_float(self): # invalid args self.assertRaises(TypeError, posix.scandir, -1.0) @unittest.skipUnless(posix.scandir in os.supports_fd, "test needs fd support for posix.scandir()") def test_scandir_fd(self): fd = posix.open(posix.getcwd(), posix.O_RDONLY) self.addCleanup(posix.close, fd) self._test_scandir(fd) self.assertEqual( sorted(posix.scandir('.')), sorted(posix.scandir(fd))) # call 2nd time to test rewind self.assertEqual( sorted(posix.scandir('.')), sorted(posix.scandir(fd))) @unittest.skipUnless(posix.scandir in os.supports_dir_fd, "test needs dir_fd support for os.scandir()") def test_scandir_dir_fd(self): relpath = 'relative_path' with support.temp_dir() as parent: fullpath = os.path.join(parent, relpath) with support.temp_dir(path=fullpath): support.create_empty_file(os.path.join(parent, 'a')) support.create_empty_file(os.path.join(fullpath, 'b')) fd = posix.open(parent, posix.O_RDONLY) self.addCleanup(posix.close, fd) self.assertEqual( sorted(posix.scandir(relpath, dir_fd=fd)), sorted(posix.scandir(fullpath))) # check that fd is still useful self.assertEqual( sorted(posix.scandir(relpath, dir_fd=fd)), sorted(posix.scandir(fullpath))) -- Akira _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com