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Re: Operator Precedence/Boolean Logic

Path csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From Andreas Röhler <andreas.roehler@online.de>
Newsgroups comp.lang.python
Subject Re: Operator Precedence/Boolean Logic
Date Thu, 23 Jun 2016 08:34:41 +0200
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On 23.06.2016 06:47, Lawrence D’Oliveiro wrote:
> On Thursday, June 23, 2016 at 3:12:52 PM UTC+12, Larry Hudson wrote:
>> On 06/22/2016 12:42 AM, Lawrence D’Oliveiro wrote:
>>> * boolean operators don’t have to operate on boolean values. The
>>>    language spec
>>>    <https://docs.python.org/3/reference/expressions.html#boolean-operations>
>>>    says:
>>>
>>>      “...the following values are interpreted as false: False, None, numeric
>>>      zero of all types, and empty strings and containers (including strings,
>>>      tuples, lists, dictionaries, sets and frozensets). All other values are
>>>      interpreted as true.”
>>>
>>> I feel that’s a needlessly complicated rule. It would have been simpler if
>>> boolean operators (and conditional expressions like in if-statements and
>>> while-statements) only allowed values of boolean types. But that’s one of
>>> the few warts in the design of Python...
>> Wart??  I *strongly* disagree.  I find it one of the strengths of Python,
>> it enhances Python's expressiveness.
> Tightening it up would rule out a whole class of common errors, from misunderstanding (or forgetting) the rule about what exactly gets interpreted as true and what as false <https://bugs.python.org/issue13936> <http://stackoverflow.com/questions/28116931/datetime-time0-0-evaluates-as-false-in-boolean-context>.

Indeed, why should the result of 4 - 4 have a different truth-value than 
4 - 3 ?
This implementation seems to be a legacy from languages without boolean 
types.

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Thread

Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-21 20:40 -0700
  Re: Operator Precedence/Boolean Logic Ben Finney <ben+python@benfinney.id.au> - 2016-06-22 13:59 +1000
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:19 -0700
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:20 -0700
  Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-22 16:02 +1000
  Re: Operator Precedence/Boolean Logic Christian Gollwitzer <auriocus@gmx.de> - 2016-06-22 08:26 +0200
    Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-22 10:14 +0300
      Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:21 -0700
  Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-22 00:42 -0700
    Re: Operator Precedence/Boolean Logic Larry Hudson <orgnut@yahoo.com> - 2016-06-22 20:12 -0700
      Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-23 13:59 +1000
        Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:23 -0700
        Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 09:58 +0200
          Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 11:16 +0300
            Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-23 01:53 -0700
              Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:10 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:27 +0200
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:53 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 12:54 +0200
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 13:59 +0300
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 13:15 +0200
                Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-23 15:05 +0300
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-23 22:13 +1000
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-23 02:44 -0700
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:57 +0300
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-24 22:38 -0700
                Re: Operator Precedence/Boolean Logic Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-06-25 09:46 +0300
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:01 +0200
          Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 19:39 +1000
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 12:21 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-23 22:37 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 15:24 +0200
                Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-23 09:26 -0400
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-24 02:43 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-24 01:49 +1000
        Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-25 11:56 +0300
      Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-06-22 21:47 -0700
        Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-22 22:00 -0700
        Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 08:34 +0200
          Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 09:46 +0300
          Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 17:05 +1000
            Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 10:17 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 18:48 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 11:23 +0200
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-23 21:45 +1000
                Re: Operator Precedence/Boolean Logic Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-06-23 14:08 +0200
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 14:22 +0200
            Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 10:23 +0200
            Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 10:32 +0200
              Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 19:17 +1000
                Re: Operator Precedence/Boolean Logic Marko Rauhamaa <marko@pacujo.net> - 2016-06-23 12:46 +0300
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 12:19 +0200
                Re: Operator Precedence/Boolean Logic Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-06-26 11:01 +1200
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-29 03:21 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-06-29 21:06 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-29 23:08 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-29 06:30 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-30 09:40 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-06-30 09:01 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-01 03:22 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-15 22:48 -0700
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-15 22:58 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 19:14 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 20:16 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-16 20:46 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-16 21:02 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 00:26 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 05:33 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 02:27 +1000
                Re: Operator Precedence/Boolean Logic MRAB <python@mrabarnett.plus.com> - 2016-07-16 17:58 +0100
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 20:43 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 14:05 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 23:44 -0700
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 23:59 -0700
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 17:33 +1000
                Re: Operator Precedence/Boolean Logic Lawrence D’Oliveiro <lawrencedo99@gmail.com> - 2016-07-17 00:44 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 20:04 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 21:02 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-17 08:00 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-18 01:58 +1000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-18 02:01 +1000
                Re: Operator Precedence/Boolean Logic Chris Angelico <rosuav@gmail.com> - 2016-07-17 03:06 +1000
                Re: Operator Precedence/Boolean Logic Rustom Mody <rustompmody@gmail.com> - 2016-07-16 05:15 -0700
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-07-17 02:36 +1000
                Re: Operator Precedence/Boolean Logic Grant Edwards <grant.b.edwards@gmail.com> - 2016-06-29 15:00 +0000
                Re: Operator Precedence/Boolean Logic Jon Ribbens <jon+usenet@unequivocal.eu> - 2016-06-29 15:05 +0000
                Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve@pearwood.info> - 2016-06-30 09:44 +1000
                Re: Operator Precedence/Boolean Logic Andreas Röhler <andreas.roehler@online.de> - 2016-06-23 11:51 +0200
        Re: Operator Precedence/Boolean Logic Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-06-23 17:20 +1000
        Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-23 09:18 -0400
      Re: Operator Precedence/Boolean Logic Christian Gollwitzer <auriocus@gmx.de> - 2016-06-23 09:11 +0200
    Re: Operator Precedence/Boolean Logic Elizabeth Weiss <cake240@gmail.com> - 2016-06-22 21:22 -0700
  Fwd: Operator Precedence/Boolean Logic Jorge Gimeno <jlgimeno71@gmail.com> - 2016-06-21 20:56 -0700
  Re: Operator Precedence/Boolean Logic Random832 <random832@fastmail.com> - 2016-06-22 10:10 -0400
  Re: Operator Precedence/Boolean Logic Erik <python@lucidity.plus.com> - 2016-06-22 20:43 +0100

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