gh-87063: Add closed attribute to multiprocessing.Process

Doc/library/multiprocessing.rst

@@ -706,6 +706,12 @@ The :mod:`multiprocessing` package mostly replicates the API of the
        >>> p.exitcode == -signal.SIGTERM
        True
 
+   .. attribute:: closed
+
+      Boolean indicating whether the process has been closed via :meth:`close`.
+
+      .. versionadded:: 3.14
+
 .. exception:: ProcessError
 
    The base class of all :mod:`multiprocessing` exceptions.

Lib/multiprocessing/process.py

@@ -169,6 +169,13 @@ def is_alive(self):
             _children.discard(self)
             return False
 
+    @property
+    def closed(self):
+        '''
+        Return whether process is closed
+        '''
+        return self._closed
+
     def close(self):
         '''
         Close the Process object.

Lib/test/_test_multiprocessing.py

@@ -659,20 +659,24 @@ def test_close(self):
         self.assertEqual(p.is_alive(), True)
         # Child is still alive, cannot close
         with self.assertRaises(ValueError):
+            self.assertFalse(p.closed)
             p.close()
+            self.assertTrue(p.closed)
 
         q.put(None)
         p.join()
         self.assertEqual(p.is_alive(), False)
         self.assertEqual(p.exitcode, 0)
         p.close()
+        self.assertTrue(p.closed)
         with self.assertRaises(ValueError):
             p.is_alive()
         with self.assertRaises(ValueError):
             p.join()
         with self.assertRaises(ValueError):
             p.terminate()
         p.close()
+        self.assertTrue(p.closed)
 
         wr = weakref.ref(p)
         del p

Misc/NEWS.d/next/Library/2024-10-22-19-52-15.gh-issue-87063.fR-wJa.rst

@@ -0,0 +1,2 @@
+Allow to determine whether a :class:`multiprocessing.Process` has been closed
+via the :attr:`~multiprocessing.Process.closed` attribute.