Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Case Statements
Date: Thu, 17 Mar 2016 17:30:42 +1100
Lines: 47
Message-ID: <mailman.256.1458196245.12893.python-list@python.org>
References: <f30500db-19cb-4de8-81f1-6eb77c28b3b4@googlegroups.com> <30502a2e-0bad-4b0f-a1e8-a2b40b0d7ab9@googlegroups.com> <mailman.181.1458102409.12893.python-list@python.org> <ncb4e0$op1$1@dont-email.me> <ncb6jk$rrm$1@ger.gmane.org> <56E928D4.3000701@rece.vub.ac.be> <ncbac2$qtk$1@ger.gmane.org> <56E93ADD.9040500@rece.vub.ac.be> <ncbeq6$vq$1@ger.gmane.org> <56E961C9.7040008@rece.vub.ac.be> <ncbp2b$ge6$3@ger.gmane.org> <56E97B60.3060402@rece.vub.ac.be> <ncc4tb$6kj$1@ger.gmane.org> <56E9A66E.4030905@rece.vub.ac.be> <mailman.253.1458170061.12893.python-list@python.org> <56e9f7f9$0$1597$c3e8da3$5496439d@news.astraweb.com> <mailman.254.1458174695.12893.python-list@python.org> <56ea0e4f$0$1585$c3e8da3$5496439d@news.astraweb.com> <dkuujrFcplnU1@mid.individual.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
In-Reply-To: <dkuujrFcplnU1@mid.individual.net>
Precedence: list
Xref: csiph.com comp.lang.python:105068

On Thu, Mar 17, 2016 at 4:45 PM, Gregory Ewing
<greg.ewing@canterbury.ac.nz> wrote:
> Steven D'Aprano wrote:
>>
>> On Thu, 17 Mar 2016 11:31 am, Chris Angelico wrote:
>>
>>>    orig = globals()[cls.__name__]
>>
>>
>> I wouldn't want to rely on it working with decorator syntax either. Even
>> if
>> it does now, I'm not sure that's a language guarantee.
>
>
> The following idiom relies on similar behaviour:
>
>     @property
>     def x(self):
>         return self._x
>
>     @x.setter
>     def x(self, value):
>         self._x = value
>
> That's taken from the official docs, so I don't think
> this is likely to change any time soon.

Ooh, didn't think of that. So maybe it's a language guarantee that
hasn't been written down somewhere, and the "func = deco(func)"
version is a known-imperfect-equivalent, same as "for x in iter: yield
x" is an imperfect equivalent for "yield from iter".

It would be possible to support @x.setter by simply guaranteeing that
the decorator expression is evaluated prior to the function creation:

_tmp = x.setter # but without using an actual name
def x(self, value):
    self._x = value
x = _tmp(x)

But I doubt the language needs to go to this level of finickiness. In
fact, all it really needs is an acknowledgement that there are corner
cases:

http://bugs.python.org/issue26576

ChrisA