classification
Title: classes should have mutable docstrings
Type: behavior Stage: resolved
Components: Interpreter Core Versions: Python 3.3
process
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: Nosy List: eric.snow, michael.foord, ncoghlan, python-dev
Priority: normal Keywords: patch

Created on 2011-08-17 16:32 by eric.snow, last changed 2011-08-17 17:04 by python-dev. This issue is now closed.

Files
File name Uploaded Description Edit
mutable_class_docstrings.diff eric.snow, 2011-08-17 16:32 review
Messages (2)
msg142287 - (view) Author: Eric Snow (eric.snow) * (Python committer) Date: 2011-08-17 16:32
Apparently docstrings for classes are immutable:

>>> class X:
...     "some doc"
...
>>> X.__doc__
'some doc'
>>> X.__doc__ = "another doc"
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
AttributeError: attribute '__doc__' of 'type' objects is not writable

That is on 3.3, but apparently it's the case all the way back to 2.2.
I mentioned this on python-list and several people indicated that it
should be an unnecessary restriction [1].  I also found that this only impacts classes that do not have a custom metaclass.

Regardless, it looks like this is something that no one has take the time to address but would be nice to have done [2][3].  I found that the type_getset for __doc__ does not have a getter:

http://hg.python.org/cpython/file/default/Objects/typeobject.c#l634

I have attached a patch that adds one and fixes the problem.  "make test" passed after the fix.


[1] http://mail.python.org/pipermail/python-list/2011-June/1274079.html
[2] http://mail.python.org/pipermail/python-ideas/2011-June/010462.html
[3] http://mail.python.org/pipermail/python-ideas/2011-August/011185.html
msg142288 - (view) Author: Roundup Robot (python-dev) Date: 2011-08-17 17:04
New changeset ed2511c23dae by Benjamin Peterson in branch 'default':
make __doc__ mutable on heaptypes (closes #12773)
http://hg.python.org/cpython/rev/ed2511c23dae
History
Date User Action Args
2011-08-17 17:04:29python-devsetstatus: open -> closed

nosy: + python-dev
messages: + msg142288

resolution: fixed
stage: resolved
2011-08-17 16:32:38eric.snowcreate