gh-130425: Add "Did you mean [...]" suggestions for del obj.attr

Doc/whatsnew/3.15.rst

@@ -175,6 +175,20 @@ Other language changes
 * Several error messages incorrectly using the term "argument" have been corrected.
   (Contributed by Stan Ulbrych in :gh:`133382`.)
 
+* The interpreter now provides helpful suggestions when :func:`delattr` fails due to a missing attribute. When an attribute name that closely resembles an existing attribute is used, the interpreter will suggest the correct attribute name in the error message. For example:
+
+.. doctest::
+
+   >>> class A:
+   ...     pass
+   >>> a = A()
+   >>> a.abcde = 1
+   >>> del a.abcdf
+   Traceback (most recent call last):
+     ...
+   AttributeError: 'A' object has no attribute 'abcdf'. Did you mean: 'abcde'?
+
+(Contributed by [sobolevn] and Pranjal Prajapati in :gh:`136588`.)
 
 
 New modules

Lib/test/test_traceback.py

@@ -4200,9 +4200,10 @@ class B:
             def method(self, name):
                 getattr(self, name)
 
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, '_blach')))
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, '_luch')))
-        self.assertIn("'_bluch'", self.get_suggestion(partial(B().method, 'bluch')))
+        obj = B()
+        self.assertIn("'_bluch'", self.get_suggestion(partial(obj.method, '_blach')))
+        self.assertIn("'_bluch'", self.get_suggestion(partial(obj.method, '_luch')))
+        self.assertIn("'_bluch'", self.get_suggestion(partial(obj.method, 'bluch')))
 
 
 class DelattrSuggestionTests(BaseSuggestionTests):

Objects/dictobject.c

@@ -6939,7 +6939,7 @@ store_instance_attr_lock_held(PyObject *obj, PyDictValues *values,
         PyErr_Format(PyExc_AttributeError,
                         "'%.100s' object has no attribute '%U'",
                         Py_TYPE(obj)->tp_name, name);
-        _PyObject_SetAttributeErrorContext(obj, name);
+        (void)_PyObject_SetAttributeErrorContext(obj, name);
         return -1;
     }