Path: csiph.com!usenet.pasdenom.info!news.albasani.net!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python.ml.bruno.dupuis@lisael.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.009
X-Spam-Evidence: '*H*': 0.98; '*S*': 0.00; 'subject:code': 0.07; 'python': 0.09; 'difference,': 0.09; 'bug': 0.10; 'def': 0.10; 'dec': 0.15; '*why*': 0.16; 'afaik.': 0.16; 'bug,': 0.16; 'subject:dead': 0.16; 'wed,': 0.16; 'wrote:': 0.17; 'pointed': 0.17; '>>>': 0.18; 'header:In-Reply-To:1': 0.25; 'header:User- Agent:1': 0.26; 'am,': 0.27; '-0700,': 0.29; "d'aprano": 0.29; 'steven': 0.29; "i'm": 0.29; 'keyword': 0.30; 'could': 0.32; 'certain': 0.33; 'to:addr:python-list': 0.33; 'subject:?': 0.35; 'there': 0.35; 'received:org': 0.36; 'should': 0.36; 'charset:us- ascii': 0.36; 'subject:: ': 0.38; 'to:addr:python.org': 0.39; 'think': 0.40; 'days': 0.60; 'content-disposition:inline': 0.60; 'between': 0.63; 'believe': 0.69; 'glad': 0.86
Date: Wed, 5 Dec 2012 19:24:13 +0100
From: Bruno Dupuis <python.ml.bruno.dupuis@lisael.org>
To: python-list@python.org
Subject: Re: why does dead code costs time?
References: <mailman.496.1354722393.29569.python-list@python.org> <50bf85c0$0$29994$c3e8da3$5496439d@news.astraweb.com> <CALwzidnEgW3ksKeXAuv-=TOseMRZ2vzFAUL89q1A+QAMr64KAQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALwzidnEgW3ksKeXAuv-=TOseMRZ2vzFAUL89q1A+QAMr64KAQ@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.516.1354731848.29569.python-list@python.org>
Lines: 29
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1354731848 news.xs4all.nl 6973 [2001:888:2000:d::a6]:35814
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:34309

On Wed, Dec 05, 2012 at 10:59:26AM -0700, Ian Kelly wrote:
> On Wed, Dec 5, 2012 at 10:34 AM, Steven D'Aprano
> <steve+comp.lang.python@pearwood.info> wrote:
> > The difference is almost certain between the LOAD_CONST and the
> > LOAD_GLOBAL.
> >
> > As to *why* there is such a difference, I believe that's a leftover from
> > early Python days when None was not a keyword and could be reassigned.
> 
> I think this should even be considered a bug, not just a missing
> optimization.  Consider:

This is definitely a bug

> >>> globals()['None'] = 42
> >>> def f(x):
> ...     return None
> ...     print(x)
> ...
> >>> f('test')
> 42

This one is pretty scary

The difference between `return None` and `return` leads to inconsistency and
is in contradiction with the specs, AFAIK. I'm glad we pointed this out.

-- 
Bruno Dupuis