Description

assignee = None
closed_at = None
created_at = <Date 2021-04-15.16:31:31.975>
labels = ['interpreter-core', 'type-feature', '3.8', '3.9', '3.10']
title = 'Fix the AttributeError message for deletion of a missing attribute'
updated_at = <Date 2021-04-18.05:53:26.612>
user = 'https://github.com/maggyero'

activity = <Date 2021-04-18.05:53:26.612>
actor = 'rhettinger'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2021-04-15.16:31:31.975>
creator = 'maggyero'
dependencies = []
files = []
hgrepos = []
issue_num = 43857
keywords = ['patch']
message_count = 1.0
messages = ['391140']
nosy_count = 3.0
nosy_names = ['rhettinger', 'pablogsal', 'maggyero']
pr_nums = ['25424']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43857'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

Activity

1. maggyero commented on Apr 15, 2021

   

   maggyeromannequin

   on Apr 15, 2021

   MannequinAuthor

   More actions

   Compare the AttributeError messages in this interactive Python session:

   >>> class A:
   ...     y = 0
   ...     __slots__ = ('z',)
   ... 
   >>> A().x
   […]
   AttributeError: 'A' object has no attribute 'x'
   >>> A().x = 1
   […]
   AttributeError: 'A' object has no attribute 'x'
   >>> del A().x
   […]
   AttributeError: 'A' object has no attribute 'x'
   >>> A().y
   0
   >>> A().y = 2
   […]
   AttributeError: 'A' object attribute 'y' is read-only
   >>> del A().y
   […]
   AttributeError: 'A' object attribute 'y' is read-only
   >>> A().z
   […]
   AttributeError: z
   >>> A().z = 3
   >>> del A().z
   […]
   AttributeError: z

   with the `AttributeError` messages in that one:
   

   >>> class B: pass
   ... 
   >>> B().x
   […]
   AttributeError: 'B' object has no attribute 'x'
   >>> B().x = 1
   >>> del B().x
   […]
   AttributeError: x

   The message AttributeError: x from del B().x does not feel right. I expect this message to be the same as the message AttributeError: 'B' object has no attribute 'x' from B().x, since in both cases the object B() has no attribute 'x'.

   I have checked on PyPy 7.3.3 (Python 3.7.9) and it uses the expected message AttributeError: 'B' object has no attribute 'x' from B().x for del B().x. So this confirms my initial suspicion.

   ----

   In CPython, the AttributeError message for attribute retrieval is implemented here (except for slot retrieval):

       if (!suppress) {
           PyErr_Format(PyExc_AttributeError,
                        "'%.50s' object has no attribute '%U'",
                        tp->tp_name, name);
       }

   And the AttributeError messages for attribute assignment and deletion are implemented here (except for slot deletion):

       if (dict == NULL) {
           dictptr = _PyObject_GetDictPtr(obj);
           if (dictptr == NULL) {
               if (descr == NULL) {
                   PyErr_Format(PyExc_AttributeError,
                                "'%.100s' object has no attribute '%U'",
                                tp->tp_name, name);
               }
               else {
                   PyErr_Format(PyExc_AttributeError,
                                "'%.50s' object attribute '%U' is read-only",
                                tp->tp_name, name);
               }
               goto done;
           }
           res = _PyObjectDict_SetItem(tp, dictptr, name, value);
       }
       else {
           Py_INCREF(dict);
           if (value == NULL)
               res = PyDict_DelItem(dict, name);
           else
               res = PyDict_SetItem(dict, name, value);
           Py_DECREF(dict);
       }
       if (res < 0 && PyErr_ExceptionMatches(PyExc_KeyError))
           PyErr_SetObject(PyExc_AttributeError, name);

   So it is the last line PyErr_SetObject(PyExc_AttributeError, name); that would be updated. Note that _PyObjectDict_SetItem delegates to PyDict_DelItem (if value is NULL) or PyDict_SetItem (if value is not NULL), and that only PyDict_DelItem can set an exception PyExc_KeyError, which is then translated to an exception PyExc_AttributeError in the last line.
2. maggyero

   added

   3.7 (EOL)end of lifeend of life

   3.10 (EOL)end of lifeend of life

   3.8 (EOL)end of lifeend of life

   3.9 (EOL)end of lifeend of life

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   type-featureA feature request or enhancementA feature request or enhancement

   on Apr 15, 2021
3. terryjreedy

   removed

   3.7 (EOL)end of lifeend of life

   on Apr 16, 2021
4. ezio-melotti

   transferred this issue fromon Apr 10, 2022
5. furkanonder commented on May 8, 2023

   

   furkanonder

   on May 8, 2023

   Contributor

   More actions

   @JelleZijlstra Issue seems to be resolved. We can close the issue.
6. pablogsal

   closed this as completedon May 9, 2023

Issue actions