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Re: 'is not' or '!='

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On Mon, 18 Aug 2014 23:53:49 +0300, Marko Rauhamaa wrote:

> "ElChino" <elchino@cnn.cn>:
> 
>> A newbie question to you; what is the difference between statements
>> like:
>>  if x is not None:
>> and if x != None:
> 
> Do the following: take two $10 bills. Hold one bill in the left hand,
> hold the other bill in the right hand.
> 
> Now, the bill in the left hand "is not" the bill in the right hand.
> However, the bill in the left hand "==" the bill in the right hand.
> 
>> Without any context, which one should be preferred?
>> IMHO, the latter is more readable.
> 
> In almost all cases, both tests would result in the same behavior.
> However, the "is not" test is conceptually the correct one since you
> want to know if x is the one and only None object. You don't want to be
> fooled by an imposter object that simply looks like the None object.
> Frankly, I don't know of any other object that is "==" to the None
> object except None itself, but such objects could possible exist.
> 
> 
> Marko

Depending on context you may 'Want' 0 to be equal to none
however as far as python is concerned it is not.




-- 
"Why must you tell me all your secrets when it's hard enough to love
you knowing nothing?"
		-- Lloyd Cole and the Commotions

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'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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