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Re: code review

References <mailman.1623.1340939177.4697.python-list@python.org> <mailman.1659.1341089444.4697.python-list@python.org> <4ff0f8e0$0$29988$c3e8da3$5496439d@news.astraweb.com> <m73mrb.cke@spenarnc.xs4all.nl> <jtq9rn$tsp$1@dough.gmane.org>
From Ian Kelly <ian.g.kelly@gmail.com>
Date 2012-07-14 03:26 -0600
Subject Re: code review
Newsgroups comp.lang.python
Message-ID <mailman.2112.1342258047.4697.python-list@python.org> (permalink)

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On Fri, Jul 13, 2012 at 5:09 PM, Terry Reedy <tjreedy@udel.edu> wrote:
>
>> From now on, for each operator I would have to remember wether it
>> is a supposedly comparison operator or not.
>
>
> I believe the following rule is true: if a op b is True or False raises,

I don't follow.  Raises what?

> then op is a potentially chained comparison operation. They are (not) equal
> (and (not) is), the 4 order comparisons, and (not) in. 'in' should be the
> only surprise and most confusing.
>>>> 1 < 3 in {3,4}
> True
>>>> 3 in {3,4} < {4}
> False
>
> 'and' and 'or' are not included because they do not always return a bool,
> and indeed, they are not binary operators in the usual sense because of
> short-circuiting.

The only one of those operators that can be said to always return a
bool is "is (not)".  The others (apart from "and" and "or") all can be
overloaded to return anything you want (for example, sqlalchemy
overloads them to return expression objects that are later compiled
into SQL), and chaining still occurs regardless of the types they are
applied to.

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code review "Littlefield, Tyler" <tyler@tysdomain.com> - 2012-06-28 20:57 -0600
  Re: code review alex23 <wuwei23@gmail.com> - 2012-06-28 20:58 -0700
    Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-06-29 07:31 +0000
      Re: code review Chris Angelico <rosuav@gmail.com> - 2012-06-29 17:42 +1000
      Re: code review "Littlefield, Tyler" <tyler@tysdomain.com> - 2012-06-29 09:03 -0600
        Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-29 19:41 +0000
          Re: code review MRAB <python@mrabarnett.plus.com> - 2012-06-29 21:09 +0100
          Re: code review "Martin P. Hellwig" <martin.hellwig@gmail.com> - 2012-06-29 13:27 -0700
            Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-29 20:43 +0000
              Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-06-29 19:02 -0400
              Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-06-29 23:02 -0400
          Re: code review "Littlefield, Tyler" <tyler@tysdomain.com> - 2012-06-29 14:49 -0600
            Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 09:31 +0000
              Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 09:36 +0000
          Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-06-30 02:28 +0000
            Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 09:22 +0000
          Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-06-29 23:00 -0400
        Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 10:04 +0000
          Re: code review Peter Otten <__peter__@web.de> - 2012-06-30 12:29 +0200
            Re: code review Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-06-30 20:39 +0200
              Re: code review Thomas Jollans <t@jollybox.de> - 2012-06-30 21:38 +0200
                Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 20:30 +0000
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-06-30 22:50 +0200
                Re: code review Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2012-06-30 23:07 +0200
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-06-30 23:35 +0200
                Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-06-30 17:47 -0400
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-01 00:05 +0200
                Re: code review Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2012-07-01 01:03 +0200
                Re: code review Ben Finney <ben+python@benfinney.id.au> - 2012-07-01 10:08 +1000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 10:37 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-01 03:23 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 13:48 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-01 06:54 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 16:59 +1000
                Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-07-01 05:55 -0400
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 01:26 +0000
                Re: code review Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-07-13 12:30 +0000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-13 15:04 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-14 01:36 +1000
                Re: code review rusi <rustompmody@gmail.com> - 2012-07-13 09:24 -0700
                Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-13 16:39 -0400
                Re: code review Duncan Booth <duncan.booth@invalid.invalid> - 2012-07-16 10:43 +0000
                Re: code review Ben Finney <ben+python@benfinney.id.au> - 2012-07-16 21:34 +1000
                Re: code review Albert van der Horst <albert@spenarnc.xs4all.nl> - 2012-07-17 10:54 +0000
                Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-07-13 19:09 -0400
                Re: code review Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-14 03:26 -0600
                Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-07-14 16:42 -0400
                Re: code review rusi <rustompmody@gmail.com> - 2012-06-30 21:07 -0700
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 14:20 +1000
                Re: code review Ben Finney <ben+python@benfinney.id.au> - 2012-07-01 17:28 +1000
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-01 09:46 +0200
                Re: code review HoneyMonster <nobody@someplace.invalid> - 2012-07-01 20:53 +0000
                Re: code review Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-01 05:18 -0400
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 00:41 +0000
                Re: code review Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-01 21:40 -0400
                Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-01 13:41 -0400
                Re: code review John O'Hagan <research@johnohagan.com> - 2012-07-02 14:43 +1000
                Re: Re: code review Evan Driscoll <driscoll@cs.wisc.edu> - 2012-06-30 23:45 -0500
                Re: Re: code review Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-07-01 08:57 +0200
                Re: code review Alister <alister.ware@ntlworld.com> - 2012-07-01 09:54 +0000
                Re: Re: code review Evan Driscoll <driscoll@cs.wisc.edu> - 2012-07-01 10:48 -0500
                Re: Re: code review lars van gemerden <lars@rational-it.com> - 2012-07-06 04:22 -0700
                Re: Re: code review lars van gemerden <lars@rational-it.com> - 2012-07-06 04:22 -0700
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-06 13:58 +0000
                Re: code review Roy Smith <roy@panix.com> - 2012-07-13 08:32 -0700
                Re: code review Evan Driscoll <driscoll@cs.wisc.edu> - 2012-06-30 23:57 -0500
                Re: code review Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-07-01 09:04 +0200
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-01 02:06 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 12:20 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-01 04:17 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 14:23 +1000
                Re: code review Steven D'Aprano <steve+usenet@pearwood.info> - 2012-07-01 06:27 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 16:33 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 01:28 +0000
                Re: code review Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-01 21:50 -0400
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 07:29 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-02 12:04 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 08:11 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-02 18:20 +1000
                Re: code review Rick Johnson <rantingrickjohnson@gmail.com> - 2012-07-02 08:57 -0700
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-03 02:42 +1000
                Re: code review Rick Johnson <rantingrickjohnson@gmail.com> - 2012-07-02 11:22 -0700
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-02 21:06 +0200
                Re: code review Rick Johnson <rantingrickjohnson@gmail.com> - 2012-07-02 12:35 -0700
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-03 07:57 +1000
                Re: code review Neil Cerutti <neilc@norwich.edu> - 2012-07-03 12:19 +0000
                Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-02 01:20 -0400
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-02 16:41 +0200
                Re: code review Terry Reedy <tjreedy@udel.edu> - 2012-07-02 11:33 -0400
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-01 09:35 +0200
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-02 00:43 +0000
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-02 16:26 +0200
                Re: code review Rick Johnson <rantingrickjohnson@gmail.com> - 2012-07-02 08:16 -0700
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-03 02:55 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-03 00:57 +0000
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-03 11:22 +1000
                Re: code review John O'Hagan <research@johnohagan.com> - 2012-07-03 12:25 +1000
                Re: code review Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-03 04:11 +0000
                Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-03 02:09 -0400
                Re: code review Roy Smith <roy@panix.com> - 2012-07-03 08:33 -0400
                Re: code review Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-03 16:53 +0100
                Re: code review Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-03 17:32 -0400
                Re: code review rusi <rustompmody@gmail.com> - 2012-07-02 22:10 -0700
                Re: code review Ben Finney <ben+python@benfinney.id.au> - 2012-07-03 15:46 +1000
                Re: code review John O'Hagan <research@johnohagan.com> - 2012-07-04 00:59 +1000
                Re: code review Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-03 16:50 +0100
                Re: code review Paul Rudin <paul.nospam@rudin.co.uk> - 2012-07-04 10:29 +0100
                Re: code review Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-04 17:25 +0100
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-04 01:53 +1000
                Re: code review Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-03 17:05 +0100
                Re: code review Dave Angel <d@davea.name> - 2012-07-03 16:13 -0400
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-04 07:54 +1000
                Re: code review Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-04 09:28 +0100
                Re: code review rusi <rustompmody@gmail.com> - 2012-06-30 19:37 -0700
                Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-01 09:25 +1000
                Re: code review Thomas Jollans <t@jollybox.de> - 2012-07-01 01:50 +0200
                Re: code review "Martin P. Hellwig" <martin.hellwig@gmail.com> - 2012-06-30 14:48 -0700
                Re: code review Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-02 13:16 -0600
            Re: code review Alister <alister.ware@ntlworld.com> - 2012-06-30 20:25 +0000
          Re: code review Kushal Kumaran <kushal.kumaran+python@gmail.com> - 2012-07-03 23:23 +0530
            Re: code review John Gordon <gordon@panix.com> - 2012-07-03 18:18 +0000
              Re: code review Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-03 12:27 -0600
              Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-04 07:51 +1000
          Re: code review Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-03 12:19 -0600
          Re: code review kushal.kumaran+python@gmail.com - 2012-07-04 08:27 +0530
          Re: code review Chris Angelico <rosuav@gmail.com> - 2012-07-04 13:53 +1000
          Re: code review Simon Cropper <simoncropper@fossworkflowguides.com> - 2012-07-04 14:55 +1000
          Re: code review "Littlefield, Tyler" <tyler@tysdomain.com> - 2012-07-03 23:39 -0600
            Re: code review alex23 <wuwei23@gmail.com> - 2012-07-03 23:17 -0700
              Re: code review rusi <rustompmody@gmail.com> - 2012-07-04 00:05 -0700
          Apology for OT posts (was: code review) John O'Hagan <research@johnohagan.com> - 2012-07-06 12:06 +1000
          Re: Apology for OT posts Simon Cropper <simoncropper@fossworkflowguides.com> - 2012-07-06 15:30 +1000
          Re: Apology for OT posts Chris Angelico <rosuav@gmail.com> - 2012-07-06 17:45 +1000
          Re: Apology for OT posts Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-06 10:37 +0100

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