gh-120057: Add os.environ.refresh() method

Author: vstinner

Doc/library/os.rst

@@ -193,6 +193,9 @@ process and user.
    to the environment made after this time are not reflected in :data:`os.environ`,
    except for changes made by modifying :data:`os.environ` directly.
 
+   The :meth:`os.environ.refresh() <os.environ>` method updates
+   :data:`os.environ` with changes to the environment made outside Python.
+
    This mapping may be used to modify the environment as well as query the
    environment.  :func:`putenv` will be called automatically when the mapping
    is modified.
@@ -222,6 +225,9 @@ process and user.
    :data:`os.environ`, and when one of the :meth:`pop` or :meth:`clear` methods is
    called.
 
+   .. versionchanged:: 3.14
+      Added the :meth:`!os.environ.refresh()` method.
+
    .. versionchanged:: 3.9
       Updated to support :pep:`584`'s merge (``|``) and update (``|=``) operators.
 

Doc/whatsnew/3.14.rst

@@ -92,6 +92,12 @@ ast
 Added :func:`ast.compare` for comparing two ASTs.
 (Contributed by Batuhan Taskaya and Jeremy Hylton in :issue:`15987`.)
 
+os
+--
+
+* Added the :meth:`os.environ.refresh() <os.environ>` method to update
+  :data:`os.environ` with environment changes made outside Python.
+  (Contributed by Victor Stinner in :gh:`120057`.)
 
 
 Optimizations

Lib/os.py

@@ -64,6 +64,10 @@ def _get_exports_list(module):
         from posix import _have_functions
     except ImportError:
         pass
+    try:
+        from posix import _create_environ
+    except ImportError:
+        pass
 
     import posix
     __all__.extend(_get_exports_list(posix))
@@ -88,6 +92,10 @@ def _get_exports_list(module):
         from nt import _have_functions
     except ImportError:
         pass
+    try:
+        from nt import _create_environ
+    except ImportError:
+        pass
 
 else:
     raise ImportError('no os specific module found')
@@ -773,7 +781,18 @@ def __ror__(self, other):
         new.update(self)
         return new
 
-def _createenviron():
+    if _exists("_create_environ"):
+        def refresh(self):
+            environ = _create_environ()
+            if name == 'nt':
+                data = {}
+                for key, value in environ.items():
+                    data[encodekey(key)] = value
+            else:
+                data = environ
+            self._data = data
+
+def _create_environ_mapping():
     if name == 'nt':
         # Where Env Var Names Must Be UPPERCASE
         def check_str(value):
@@ -803,8 +822,8 @@ def decode(value):
         encode, decode)
 
 # unicode environ
-environ = _createenviron()
-del _createenviron
+environ = _create_environ_mapping()
+del _create_environ_mapping
 
 
 def getenv(key, default=None):

Lib/test/test_os.py

@@ -1298,6 +1298,22 @@ def test_ror_operator(self):
         self._test_underlying_process_env('_A_', '')
         self._test_underlying_process_env(overridden_key, original_value)
 
+    @unittest.skipUnless(hasattr(os.environ, 'refresh'),
+                         'need os.environ.refresh()')
+    def test_refresh(self):
+        # Use putenv() which doesn't update os.environ
+        try:
+            from posix import putenv
+        except ImportError:
+            from nt import putenv
+
+        os.environ['test_env'] = 'python_value'
+        putenv("test_env", "new_value")
+        self.assertEqual(os.environ['test_env'], 'python_value')
+
+        os.environ.refresh()
+        self.assertEqual(os.environ['test_env'], 'new_value')
+
 
 class WalkTests(unittest.TestCase):
     """Tests for os.walk()."""

Misc/NEWS.d/next/Library/2024-06-04-18-53-10.gh-issue-120057.RSD9_Z.rst

@@ -0,0 +1,3 @@
+Added the :meth:`os.environ.refresh() <os.environ>` method to update
+:data:`os.environ` with environment changes made outside Python. Patch by
+Victor Stinner.

Modules/clinic/posixmodule.c.h

@@ -16727,6 +16727,20 @@ os__supports_virtual_terminal_impl(PyObject *module)
 #endif
 
 
+/*[clinic input]
+os._create_environ
+
+Create the environment dictionary.
+[clinic start generated code]*/
+
+static PyObject *
+os__create_environ_impl(PyObject *module)
+/*[clinic end generated code: output=19d9039ab14f8ad4 input=a4c05686b34635e8]*/
+{
+    return convertenviron();
+}
+
+
 static PyMethodDef posix_methods[] = {
 
     OS_STAT_METHODDEF
@@ -16939,6 +16953,7 @@ static PyMethodDef posix_methods[] = {
     OS__PATH_LEXISTS_METHODDEF
 
     OS__SUPPORTS_VIRTUAL_TERMINAL_METHODDEF
+    OS__CREATE_ENVIRON_METHODDEF
     {NULL,              NULL}            /* Sentinel */
 };