Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!selfless.tophat.at!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <python-python-list@m.gmane.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'extracted': 0.05; 'terry': 0.07; 'contexts': 0.09; 'implicitly': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:80.91.229.12': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'received:lo.gmane.org': 0.09; 'pm,': 0.11; 'say,': 0.14; 'wrote:': 0.14; 'boolean': 0.16; 'reedy': 0.16; 'seems': 0.21; 'jan': 0.22; 'subject:list': 0.22; 'header:In-Reply-To:1': 0.22; 'ignored.': 0.29; 'to:addr:python-list': 0.32; 'header:X -Complaints-To:1': 0.34; 'there': 0.35; 'header:User-Agent:1': 0.35; 'point': 0.35; 'call,': 0.35; 'suggested': 0.35; 'response': 0.36; 'but': 0.38; 'received:org': 0.38; '[1]': 0.39; 'to:addr:python.org': 0.39; 'where': 0.39; 'header:Mime- Version:1': 0.39; 'header:Received:5': 0.40; 'details': 0.64; 'spell': 0.91
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: checking if a list is empty
Date: Sat, 14 May 2011 17:29:53 -0400
References: <mailman.1226.1304663814.9059.python-list@python.org>	<200e93c2-6b87-4113-9c6f-85815e51ea77@28g2000yqu.googlegroups.com>	<4dc4b3c5$0$29991$c3e8da3$5496439d@news.astraweb.com>	<iuvp98-446.ln1@svn.schaathun.net>	<roy-5F8DA7.08265211052011@news.panix.com>	<931adaF9g1U1@mid.individual.net>	<roy-FC7816.07362712052011@news.panix.com>	<4dcc785e$0$29980$c3e8da3$5496439d@news.astraweb.com>	<d423a455-f14e-4cb4-8744-0a49259c9c86@34g2000pru.googlegroups.com>	<4dce31b3$0$29980$c3e8da3$5496439d@news.astraweb.com>	<d72b37d6-bf1e-4cec-94e3-88baca894fd9@35g2000prp.googlegroups.com>	<mailman.1548.1305380575.9059.python-list@python.org>	<a86edee8-306b-4777-99fb-99895b512ef6@k15g2000pri.googlegroups.com>	<mailman.1551.1305388537.9059.python-list@python.org> <311327ac-2593-44d7-b19d-32533af87d4b@x38g2000pri.googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Gmane-NNTP-Posting-Host: rain.gmane.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.17) Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10
In-Reply-To: <311327ac-2593-44d7-b19d-32533af87d4b@x38g2000pri.googlegroups.com>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.12
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.1566.1305408606.9059.python-list@python.org>
Lines: 15
NNTP-Posting-Host: 82.94.164.166
X-Trace: 1305408606 news.xs4all.nl 81481 [::ffff:82.94.164.166]:44137
X-Complaints-To: abuse@xs4all.nl
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:5389

On 5/14/2011 1:43 PM, rusi wrote:

> But it seems you did not get the moral? Spelt out: "Beware of lossy
> compression!"
> [Which is also the moral of my 'proof']

I get it now. As I suggested in response to Stephen, [] and [1] spell 
False and True only in boolean contexts (if/while headers) where they 
are implicitly wrapped with a bool() call, which is to say, where their 
boolean value is extracted from them. As you point out, there is 
information loss as all other context-irrelevant details are ignored.

-- 
Terry Jan Reedy