Apply suggestions from code review

Co-authored-by: sobolevn <[email protected]>

Author: yihong0618

Lib/inspect.py

@@ -820,10 +820,8 @@ def getfile(object):
         if getattr(object, '__file__', None):
             return object.__file__
         if object.__spec__ is not None:
-            raise TypeError('{!r} is a built-in module'.format(object))
-        else:
-            raise TypeError('Custom module: {!r} cannot get source'
-                            .format(object))
+            raise TypeError(f'{object!r} is a built-in module')
+        raise TypeError(f'Custom module: {object!r} cannot get source')
     if isclass(object):
         if hasattr(object, '__module__'):
             module = sys.modules.get(object.__module__)

Lib/test/test_inspect/test_inspect.py

@@ -812,11 +812,13 @@ def test_getfile_builtin_module(self):
         self.assertStartsWith(str(e.exception), '<module')
 
     def test_getfile_custom_module(self):
-        import types
+        import re
         custom_module = types.ModuleType('custom_module')
-        with self.assertRaises(TypeError) as e:
+        msg = re.escape(
+             f'Custom module: {custom_module!r} cannot get source'
+        )
+        with self.assertRaisesRegex(TypeError, msg) as e:
             inspect.getfile(custom_module)
-        self.assertStartsWith(str(e.exception), 'Custom module')
 
     def test_getfile_builtin_class(self):
         with self.assertRaises(TypeError) as e:

Misc/NEWS.d/next/Library/2025-09-05-23-18-51.gh-issue-138542.hQ9Q04.rst

@@ -1 +1 @@
-the error message when when inspect getfile a custom module
+Fix :func:`inspect.getfile` error message for custom module objects.