diff -r 009dc81e8bc9 Lib/tempfile.py
--- a/Lib/tempfile.py	Tue Feb 05 11:34:39 2013 -0500
+++ b/Lib/tempfile.py	Tue Feb 05 20:15:19 2013 +0200
@@ -172,15 +172,18 @@
             name = next(namer)
             filename = _os.path.join(dir, name)
             try:
-                fd = _os.open(filename, _bin_openflags, 0o600)
-                fp = _io.open(fd, 'wb')
-                fp.write(b'blat')
-                fp.close()
-                _os.unlink(filename)
-                del fp, fd
+                try:
+                    fd = _os.open(filename, _bin_openflags, 0o600)
+                except FileExistsError:
+                    continue
+                try:
+                    try:
+                        _os.write(fd, b'blat')
+                    finally:
+                        _os.close(fd)
+                finally:
+                    _os.unlink(filename)
                 return dir
-            except FileExistsError:
-                pass
             except OSError:
                 break   # no point trying more names in this directory
     raise FileNotFoundError("No usable temporary directory found in %s" % dirlist)
diff -r 009dc81e8bc9 Lib/test/test_tempfile.py
--- a/Lib/test/test_tempfile.py	Tue Feb 05 11:34:39 2013 -0500
+++ b/Lib/test/test_tempfile.py	Tue Feb 05 20:15:19 2013 +0200
@@ -197,7 +197,38 @@
             # paths in this list.
 
 
-# We test _get_default_tempdir by testing gettempdir.
+# We test _get_default_tempdir some more by testing gettempdir.
+
+class TestGetDefaultTempdir(BaseTestCase):
+    """Test _get_default_tempdir()."""
+
+    def test_no_files_left_behind(self):
+        # use a private empty directory
+        with tempfile.TemporaryDirectory() as our_temp_directory:
+            # force _get_default_tempdir() to consider our empty directory
+            def our_candidate_list():
+                return [our_temp_directory]
+
+            with support.swap_attr(tempfile, "_candidate_tempdir_list",
+                                   our_candidate_list):
+                # verify our directory is empty after _get_default_tempdir()
+                tempfile._get_default_tempdir()
+                self.assertEqual(os.listdir(our_temp_directory), [])
+
+                def raise_OSError(*args, **kwargs):
+                    raise OSError()
+
+                with support.swap_attr(os, "open", raise_OSError):
+                    # test again with failing os.open()
+                    with self.assertRaises(FileNotFoundError):
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(os.listdir(our_temp_directory), [])
+
+                with support.swap_attr(os, "write", raise_OSError):
+                    # test again with failing os.write()
+                    with self.assertRaises(FileNotFoundError):
+                        tempfile._get_default_tempdir()
+                    self.assertEqual(os.listdir(our_temp_directory), [])
 
 
 class TestGetCandidateNames(BaseTestCase):