Issue 24064: Make the property doctstring writeable

I can't see any reason for property docstrings to be readonly:

    >>> p = property(doc='basic')
    >>> p.__doc__
    'basic'
    >>> p.__doc__ = 'extended'
    Traceback (most recent call last):
      File "<pyshell#46>", line 1, in <module>
        p.__doc__ = 'extended'
    AttributeError: readonly attribute

Among other things, making it writeable would simplify the ability to update the docstrings produced by namedtuple;

    Time.mtime.__doc__ = 'modification time'
    Score.max = 'all time cumulative high score for a single season'

Here is a patch. I'm not familiar with this part of the CPython source. So please tell me if there is a better way to do it. I only updated Doc/whatsnew/3.5, but other places in the documentation needs to be updated.

If make docstrings writable, it would be good to ensure that they exactly are strings. And if make the property doctstring writable, may be make other docstrings writable? It may be useful for setting the same docstring for Python implementation and C accelerator.

> If make docstrings writable, it would be good to ensure 
> that they exactly are strings.

I don't see a need for this restriction.  Even regular classes don't enforce this.

Perhaps the property class now need set the tp_clear slot?

New changeset 1e8a768fa0a5 by Raymond Hettinger in branch 'default':
Issue #24064: Property() docstrings are now writeable.
https://hg.python.org/cpython/rev/1e8a768fa0a5

New changeset bde652ae05fd by Berker Peksag in branch 'default':
Issue #24064: Add __doc__ to the example in collections.rst.
https://hg.python.org/cpython/rev/bde652ae05fd

LGTM.

An example of uncollectable loop if tp_clear is not implemented:

class A:
    @property
    def f(self): pass

A.f.__doc__ = (A.f,)

New changeset 2ddadd0e736d by Raymond Hettinger in branch 'default':
Issue #24064: Help property() support GC
https://hg.python.org/cpython/rev/2ddadd0e736d

New changeset 5262dd507ee5 by Raymond Hettinger in branch 'default':
Issue #24064:  Docuement that oroperty docstrings are now writeable.
https://hg.python.org/cpython/rev/5262dd507ee5

nosy: + berker.peksag
messages: + msg242107

keywords: + patch