Re: 'is not' or '!='

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From	Ian Kelly <ian.g.kelly@gmail.com>
Date	Tue, 19 Aug 2014 10:42:49 -0600
Subject	Re: 'is not' or '!='
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On Tue, Aug 19, 2014 at 7:12 AM, Skip Montanaro <skip@pobox.com> wrote:
> The use of "is" or "is not" is the right thing to do when the object
> of the comparison is known to be a singleton. That is true for None.
> (I suspect it's true for True and False as well, though for historical
> and idiomatic reasons "x is True" is never used.) It would also be
> true if you created a sentinel object like this:
>
> SENTINEL = []

When I need to do this, I use:

    SENTINEL = object()

It's still a singleton, and why should a sentinel be mutable?

Thread

'is not' or '!=' "ElChino" <elchino@cnn.cn> - 2014-08-18 22:35 +0200
  Re: 'is not' or '!=' MRAB <python@mrabarnett.plus.com> - 2014-08-18 21:53 +0100
  Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-18 23:53 +0300
    Re: 'is not' or '!=' "ElChino" <elchino@cnn.cn> - 2014-08-18 22:58 +0200
      Re: 'is not' or '!=' Ethan Furman <ethan@stoneleaf.us> - 2014-08-18 14:42 -0700
      Re: 'is not' or '!=' Ethan Furman <ethan@stoneleaf.us> - 2014-08-18 15:19 -0700
      Re: 'is not' or '!=' Chris Kaynor <ckaynor@zindagigames.com> - 2014-08-18 15:04 -0700
        Re: 'is not' or '!=' Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2014-08-19 11:49 +0200
      Re: 'is not' or '!=' Martin S <shieldfire@gmail.com> - 2014-08-19 14:42 +0200
      Re: 'is not' or '!=' Skip Montanaro <skip@pobox.com> - 2014-08-19 08:12 -0500
        Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-19 20:29 +0300
          Re: 'is not' or '!=' Tim Chase <python.list@tim.thechases.com> - 2014-08-19 12:34 -0500
            Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-19 21:18 +0300
          Re: 'is not' or '!=' Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-20 04:26 +1000
            Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-19 21:52 +0300
              Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-20 00:00 +0300
                Re: 'is not' or '!=' Ian Kelly <ian.g.kelly@gmail.com> - 2014-08-19 16:21 -0600
                Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-20 02:02 +0300
                Re: 'is not' or '!=' Rustom Mody <rustompmody@gmail.com> - 2014-08-20 22:03 -0700
                Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-21 08:56 +0300
            Re: 'is not' or '!=' Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-19 20:05 +0100
            Re: 'is not' or '!=' Terry Reedy <tjreedy@udel.edu> - 2014-08-19 18:23 -0400
      Re: 'is not' or '!=' Ian Kelly <ian.g.kelly@gmail.com> - 2014-08-19 10:42 -0600
        Re: 'is not' or '!=' Marko Rauhamaa <marko@pacujo.net> - 2014-08-19 20:36 +0300
      Re: 'is not' or '!=' Skip Montanaro <skip@pobox.com> - 2014-08-19 13:44 -0500
    Re: 'is not' or '!=' alister <alister.nospam.ware@ntlworld.com> - 2014-08-19 09:35 +0000
    Re: 'is not' or '!=' Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2014-08-19 11:53 +0200
  Re: 'is not' or '!=' Rustom Mody <rustompmody@gmail.com> - 2014-08-18 19:29 -0700
    Re: 'is not' or '!=' Steven D'Aprano <steve@pearwood.info> - 2014-08-19 08:36 +0000
      Re: 'is not' or '!=' Chris Angelico <rosuav@gmail.com> - 2014-08-19 18:47 +1000
      Re: 'is not' or '!=' Tim Chase <python.list@tim.thechases.com> - 2014-08-19 05:36 -0500
      Re: 'is not' or '!=' Ben Finney <ben+python@benfinney.id.au> - 2014-08-20 09:24 +1000
        Re: 'is not' or '!=' Rustom Mody <rustompmody@gmail.com> - 2014-08-19 21:01 -0700
          Re: 'is not' or '!=' Steven D'Aprano <steve@pearwood.info> - 2014-08-20 04:59 +0000
            Re: 'is not' or '!=' Rustom Mody <rustompmody@gmail.com> - 2014-08-19 22:25 -0700
              Re: 'is not' or '!=' Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-08-20 21:05 +1000
                Re: 'is not' or '!=' Chris Angelico <rosuav@gmail.com> - 2014-08-20 21:17 +1000
                Re: 'is not' or '!=' Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2014-08-21 20:31 +0200
                Re: 'is not' or '!=' Tim Chase <python.list@tim.thechases.com> - 2014-08-20 06:26 -0500
                Re: 'is not' or '!=' Chris Angelico <rosuav@gmail.com> - 2014-08-20 21:33 +1000
                Re: 'is not' or '!=' Robert Kern <robert.kern@gmail.com> - 2014-08-20 12:40 +0100
                Re: 'is not' or '!=' Rustom Mody <rustompmody@gmail.com> - 2014-08-20 05:01 -0700
  Re: 'is not' or '!=' Dan Stromberg <drsalists@gmail.com> - 2014-08-21 12:24 -0700
    Re: 'is not' or '!=' "ElChino" <elchino@cnn.cn> - 2014-08-21 21:42 +0200

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