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Oct 11, 2025
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gh-139482: Add posix._clearenv() function #139965

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gh-139482: Add posix.clearenv() function
vstinner Oct 11, 2025
4f5e2d0
Rename posix.clearenv() to posix._clearenv()
vstinner Oct 11, 2025
7c2e09e
Update NEWS entry
vstinner Oct 11, 2025
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11 changes: 11 additions & 0 deletions Lib/os.py
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,11 @@ def _get_exports_list(module):
__all__.append('_exit')
except ImportError:
pass
try:
from posix import _clearenv
__all__.append('_clearenv')
except ImportError:
pass
import posixpath as path

try:
Expand Down Expand Up @@ -768,6 +773,12 @@ def __ror__(self, other):
new.update(self)
return new

if _exists("_clearenv"):
def clear(self):
_clearenv()
self._data.clear()


def _create_environ_mapping():
if name == 'nt':
# Where Env Var Names Must Be UPPERCASE
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8 changes: 8 additions & 0 deletions Lib/test/test_os/test_os.py
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Expand Up @@ -1494,6 +1494,14 @@ def test_reload_environ(self):
self.assertNotIn(b'test_env', os.environb)
self.assertNotIn('test_env', os.environ)

def test_clearenv(self):
os.environ['REMOVEME'] = '1'
os.environ.clear()
self.assertEqual(os.environ, {})

self.assertRaises(TypeError, os.environ.clear, None)


class WalkTests(unittest.TestCase):
"""Tests for os.walk()."""
is_fwalk = False
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2025-10-11-20-03-13.gh-issue-139482.du2Stg.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Optimize :data:`os.environ.clear() <os.environ>` by calling
:manpage:`clearenv(3)` when this function is available.
Patch by Victor Stinner.
27 changes: 26 additions & 1 deletion Modules/clinic/posixmodule.c.h
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20 changes: 20 additions & 0 deletions Modules/posixmodule.c
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Expand Up @@ -13201,6 +13201,25 @@ os_unsetenv_impl(PyObject *module, PyObject *name)
#endif /* !MS_WINDOWS */


#ifdef HAVE_CLEARENV
/*[clinic input]
os._clearenv
[clinic start generated code]*/

static PyObject *
os__clearenv_impl(PyObject *module)
/*[clinic end generated code: output=2d6705d62c014b51 input=47d2fa7f323c43ca]*/
{
errno = 0;
int err = clearenv();
if (err) {
return posix_error();
}
Py_RETURN_NONE;
}
#endif


/*[clinic input]
os.strerror

Expand Down Expand Up @@ -17167,6 +17186,7 @@ static PyMethodDef posix_methods[] = {
OS_POSIX_FADVISE_METHODDEF
OS_PUTENV_METHODDEF
OS_UNSETENV_METHODDEF
OS__CLEARENV_METHODDEF
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Shouldn't this also be inside ifdef guard?

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AC handles this by creating a no-op macro

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Yeah, AC is magic :-) It just works. Look at Modules/clinic/posixmodule.c.h:

#if defined(HAVE_CLEARENV)
...
#define OS__CLEARENV_METHODDEF    \
    {"_clearenv", (PyCFunction)os__clearenv, METH_NOARGS, os__clearenv__doc__}, 
... 
#endif /* defined(HAVE_CLEARENV) */ 

...

#ifndef OS__CLEARENV_METHODDEF
    #define OS__CLEARENV_METHODDEF
#endif /* !defined(OS__CLEARENV_METHODDEF) */

OS_STRERROR_METHODDEF
OS_FCHDIR_METHODDEF
OS_FSYNC_METHODDEF
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6 changes: 6 additions & 0 deletions configure
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5 changes: 3 additions & 2 deletions configure.ac
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Expand Up @@ -5226,7 +5226,8 @@ fi

# checks for library functions
AC_CHECK_FUNCS([ \
accept4 alarm bind_textdomain_codeset chmod chown clock closefrom close_range confstr \
accept4 alarm bind_textdomain_codeset chmod chown clearenv \
clock closefrom close_range confstr \
copy_file_range ctermid dladdr dup dup3 execv explicit_bzero explicit_memset \
faccessat fchmod fchmodat fchown fchownat fdopendir fdwalk fexecve \
fork fork1 fpathconf fstatat ftime ftruncate futimens futimes futimesat \
Expand Down Expand Up @@ -8173,7 +8174,7 @@ PY_STDLIB_MOD([xxlimited_35], [test "$TEST_MODULES" = yes], [test "$ac_cv_func_d

# Determine JIT stencils header files based on target platform
JIT_STENCILS_H=""
AS_VAR_IF([enable_experimental_jit], [no],
AS_VAR_IF([enable_experimental_jit], [no],
[],
[case "$host" in
aarch64-apple-darwin*)
Expand Down
3 changes: 3 additions & 0 deletions pyconfig.h.in
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Expand Up @@ -141,6 +141,9 @@
/* Define if you have the 'chroot' function. */
#undef HAVE_CHROOT

/* Define to 1 if you have the 'clearenv' function. */
#undef HAVE_CLEARENV

/* Define to 1 if you have the 'clock' function. */
#undef HAVE_CLOCK

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