gh-160684: Normalize non-string vars in ConfigParser.items()

Lib/configparser.py

@@ -991,6 +991,8 @@ def items(self, section=_UNSET, raw=False, vars=None):
         # Update with the entry specific variables
         if vars:
             for key, value in vars.items():
+                if value is not None:
+                    value = str(value)
                 d[self.optionxform(key)] = value
         value_getter = lambda option: self._interpolation.before_get(
             self, section, option, d[option], d

Lib/test/test_configparser.py

@@ -904,6 +904,21 @@ def check_items_config(self, expected):
         with self.assertRaises(configparser.NoSectionError):
             cf.items("no such section")
 
+    def test_items_non_string_vars(self):
+        cf = self.newconfig(defaults={'default': 'original'})
+        cf.read_dict({'section': {'value': 'original'}})
+        for value in (42, 0, False):
+            for raw in (False, True):
+                with self.subTest(value=value, raw=raw):
+                    self.assertEqual(
+                        dict(cf.items('section', raw=raw, vars={
+                            'default': value,
+                            'VALUE': value,
+                            'extra': value,
+                        })),
+                        {'default': str(value), 'value': str(value)},
+                    )
+
     def test_popitem(self):
         cf = self.fromstring(
             f"""

Misc/NEWS.d/next/Library/2026-10-26-06-10-00.gh-issue-160684.vArs42.rst

@@ -0,0 +1,2 @@
+Fix :meth:`configparser.ConfigParser.items` to convert non-``None`` values
+passed in *vars* to strings, consistently with :meth:`~configparser.ConfigParser.get`.