Check for tuple in the __get__ of the new descriptor and don't cache the descriptor itself

Author: pablogsal

Lib/collections/__init__.py

@@ -459,13 +459,12 @@ def __getnewargs__(self):
     cache = _nt_itemgetters
     for index, name in enumerate(field_names):
         try:
-            tuplegetter_object, doc = cache[index]
+            doc = cache[index]
         except KeyError:
             doc = f'Alias for field number {index}'
-            tuplegetter_object = _tuplegetter(index, doc=doc)
-            cache[index] = tuplegetter_object, doc
+            cache[index] = doc
 
-        tuplegetter_object.__doc__ = doc
+        tuplegetter_object = _tuplegetter(index, doc=doc)
         class_namespace[name] = tuplegetter_object
 
     result = type(typename, (tuple,), class_namespace)

Modules/_collectionsmodule.c

@@ -2367,6 +2367,10 @@ tuplegetterdescr_get(PyObject *self, PyObject *obj, PyObject *type)
         Py_INCREF(self);
         return self;
     }
+    if (!PyTuple_Check(obj)){
+        PyErr_SetString(PyExc_TypeError, "_tuplegetter must be used with tuples");
+        return NULL;
+    }
     result = PyTuple_GetItem(obj, ((_tuplegetterobject*)self)->index);
     Py_XINCREF(result);
     return result;