Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Chris Angelico <rosuav@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Operator Precedence/Boolean Logic
Date: Sun, 17 Jul 2016 00:26:19 +1000
Lines: 30
Message-ID: <mailman.36.1468679182.2307.python-list@python.org>
References: <15997174-44d5-431c-8f90-a8d700921820@googlegroups.com> <mailman.55.1466663422.11516.python-list@python.org> <576b8a41$0$2792$c3e8da3$76491128@news.astraweb.com> <576B9B33.2030903@rece.vub.ac.be> <07e13a5d-38bf-7bfa-f45f-a24dea8e3004@online.de> <mailman.59.1466670482.11516.python-list@python.org> <576ba927$0$1504$c3e8da3$5496439d@news.astraweb.com> <87wplgfdb5.fsf@elektro.pacujo.net> <dt8gr5FkccbU1@mid.individual.net> <4c257ef7-519f-4121-b63b-fb38566072d0@googlegroups.com> <5773c832$0$1598$c3e8da3$5496439d@news.astraweb.com> <c32a4369-706b-40bc-8a8b-410b4a29df20@googlegroups.com> <57745c6d$0$1583$c3e8da3$5496439d@news.astraweb.com> <d60e179a-c244-48c1-8438-03ad63292897@googlegroups.com> <5775555f$0$22140$c3e8da3$5496439d@news.astraweb.com> <7ecde6d0-d3db-4a7a-8de6-65b398fedafe@googlegroups.com> <578a0992$0$1610$c3e8da3$5496439d@news.astraweb.com> <CAPTjJmpRO+V+6s8RebvTkUu=7DqWPbM5ycgSZkhsZ7ebsPz6Dw@mail.gmail.com> <mailman.33.1468665977.2307.python-list@python.org> <578a1436$0$1601$c3e8da3$5496439d@news.astraweb.com> <CAPTjJmqYyuvgOdZZnejdTX7f4-jHvv7FC-YrL-SAGAX2ropgBA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
X-Trace: news.uni-berlin.de 5WIXRMd81O7nljc674tiGgwC6ufG7fqF7Sgn4f/s2dEw==
Return-Path: <rosuav@gmail.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.024
X-Spam-Evidence: '*H*': 0.95; '*S*': 0.00; '16,': 0.03; 'api': 0.09; 'cc:addr:python-list': 0.09; 'bug': 0.10; 'times,': 0.13; 'value.': 0.15; '2016': 0.16; 'bug,': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'wrote:': 0.16; 'all,': 0.20; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; 'delta': 0.22; 'demonstrate': 0.23; 'sat,': 0.23; 'implemented': 0.24; 'header:In-Reply-To:1': 0.24; 'sense': 0.26; 'chris': 0.26; 'equivalent': 0.27; 'message- id:@mail.gmail.com': 0.27; 'bad.': 0.29; 'subject:/': 0.30; 'anyone': 0.32; 'point': 0.33; "d'aprano": 0.33; 'steven': 0.33; 'values.': 0.33; 'received:google.com': 0.35; 'false': 0.35; 'happened': 0.35; 'but': 0.36; 'possible': 0.36; '(and': 0.36; 'pm,': 0.36; 'subject:: ': 0.37; 'two': 0.37; 'being': 0.37; 'difference': 0.38; 'wrong': 0.38; 'does': 0.39; 'still': 0.40; 'default': 0.61; 'show': 0.62; 'real': 0.62; 'between': 0.65; "they're": 0.66; 'jul': 0.72; '9:02': 0.84; 'chrisa': 0.84; 'to:none': 0.91; 'qualitative': 0.91; 'stood': 0.93
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:cc; bh=RTzaQKbijFRktoMVQQ5W38o1+Qy751C/RKKPgm9xI2M=; b=eC9/eWLHdqcEt8bhKsLx+q4WIKNMuVrOxLorE34TF9vzlAkDwEdpJEP039YTlvWHcQ NuBU7H3f/1IcIdOiGKFJpB+rj/M0wAPg+2knD6vOhtPwA7SrHqPZlo9cTyO8dJN9Igm3 HVrr0B6oNSXYS3V3kSMLE1SMVMPluB6BAzWaUGfgOwNnzOxYgsxsVeJkwe+HJY/kAWUH 3sm4aOdWWCES4IkxHJ0D50ifAWpzY918Ca8yEy0cMpoJeW1yeu4GXBeRcCsF3Ps6svLH D47w74/nhqRdRhUoNHrTdrqVSMgKCOEUsHUI4LP/ppXHhEninQx/MqH86jrU47D3J/To XvbA==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:cc; bh=RTzaQKbijFRktoMVQQ5W38o1+Qy751C/RKKPgm9xI2M=; b=O95IxCRBux2MO9W9y2Urj3d0N001mkKZ+cxUz/jQP3Z/zqOSR6I0yEB9VlwRho+kTV sEWHGdpq0VhtdB2tFTSRKK5zkiysLdZfFINlA/oNs0wGfSF4CU94qFI7X0GMjf5Hz+wA ofbfwxfgT/39BMq6geHyT/P+JQNpGb2wSuNyjnTjPWP/dx8d4lDV8GlEyAx5IDev6hDS gpa1UEcdZLhlxfBE/DkWe7gCCOpk7EONlANoOFb5x79j6GuGHILlaNpC3wrwPFYyHtwr /zrXsQhjnlm8cXfyHwqMnatpM2UdSpCFs4pHZEwLnvvwOrUMMeBdDoOQhnZmEsevJSZK Kx9Q==
X-Gm-Message-State: ALyK8tJs3HJqu+w0gH9ugBL1iuEVLX+6tosRvH96I0RLgVbVlk8DR6t5rU/pSuOUfrAGjLz4GSm7lkNHSR4Gww==
X-Received: by 10.194.117.72 with SMTP id kc8mr4875955wjb.30.1468679180715; Sat, 16 Jul 2016 07:26:20 -0700 (PDT)
In-Reply-To: <578a1436$0$1601$c3e8da3$5496439d@news.astraweb.com>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://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: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
X-Mailman-Original-Message-ID: <CAPTjJmqYyuvgOdZZnejdTX7f4-jHvv7FC-YrL-SAGAX2ropgBA@mail.gmail.com>
X-Mailman-Original-References: <15997174-44d5-431c-8f90-a8d700921820@googlegroups.com> <mailman.55.1466663422.11516.python-list@python.org> <576b8a41$0$2792$c3e8da3$76491128@news.astraweb.com> <576B9B33.2030903@rece.vub.ac.be> <07e13a5d-38bf-7bfa-f45f-a24dea8e3004@online.de> <mailman.59.1466670482.11516.python-list@python.org> <576ba927$0$1504$c3e8da3$5496439d@news.astraweb.com> <87wplgfdb5.fsf@elektro.pacujo.net> <dt8gr5FkccbU1@mid.individual.net> <4c257ef7-519f-4121-b63b-fb38566072d0@googlegroups.com> <5773c832$0$1598$c3e8da3$5496439d@news.astraweb.com> <c32a4369-706b-40bc-8a8b-410b4a29df20@googlegroups.com> <57745c6d$0$1583$c3e8da3$5496439d@news.astraweb.com> <d60e179a-c244-48c1-8438-03ad63292897@googlegroups.com> <5775555f$0$22140$c3e8da3$5496439d@news.astraweb.com> <7ecde6d0-d3db-4a7a-8de6-65b398fedafe@googlegroups.com> <578a0992$0$1610$c3e8da3$5496439d@news.astraweb.com> <CAPTjJmpRO+V+6s8RebvTkUu=7DqWPbM5ycgSZkhsZ7ebsPz6Dw@mail.gmail.com> <mailman.33.1468665977.2307.python-list@python.org> <578a1436$0$1601$c3e8da3$5496439d@news.astraweb.com>
Xref: csiph.com comp.lang.python:111514

On Sat, Jul 16, 2016 at 9:02 PM, Steven D'Aprano <steve@pearwood.info> wrote:
> On Sat, 16 Jul 2016 08:46 pm, Chris Angelico wrote:
>
>> As Steven says,
>> the default is that they're all truthy, and onus is on the implementer
>> to demonstrate that this object is functionally equivalent to 0 or an
>> empty collection. (And it's possible for ANYONE to get that wrong - cf
>> timedelta.)
>
> I think you're thinking of time values, not timedelta values. Until
> recently, midnight was considered falsey just because it happened to be
> implemented as 0 seconds:
>
> [steve@ando ~]$ python3.3 -c "import datetime;print(bool(datetime.time(0)))"
> False
> [steve@ando ~]$ python3.6 -c "import datetime;print(bool(datetime.time(0)))"
> True
>
> That was a real bug, letting the concrete implementation show through into
> the abstract API by accident, but it's corrected now.
>
> timedelta values, being a difference between two times, have a qualitative
> difference between delta = 0 and every other value. A difference of zero is
> no difference at all, and it makes sense to make that falsey.

Umm, yes. That's the one. Time, not timedelta. My bad. Point still
stands, though - the concept of "midnight" does not truly equate to
"empty" or "zero", and that bug stood for a long time.

ChrisA