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Groups > comp.lang.python > #86192

Re: id() and is operator

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On 2/22/2015 4:25 PM, Marko Rauhamaa wrote:
> LJ <luisjosenovoa@gmail.com>:
>
>>>>> id(b[0])
>> 45855552
> [...]
>>>>> id(b[2])
>> 45855552

>> Please correct me if I am wrong, but according to this b[2] and b[0]
>> are the same object. Now,
>>
>>>>> b[0] is b[2]
>> False
>
> This is a true statement:
>
>     If X is Y, then id(X) == id(Y).
>
> However, this is generally not a true statement:
>
>     If X is Y, then id(X) is id(Y).

If X and Y exist at the *same time*, then (X is Y) == (id(X) is id(Y)). 
  Since X and Y in the example above do not exist at the same time, it 
is nonsensical to compare them.

-- 
Terry Jan Reedy

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id() and is operator LJ <luisjosenovoa@gmail.com> - 2015-02-22 09:53 -0800
  Re: id() and is operator Laura Creighton <lac@openend.se> - 2015-02-22 19:13 +0100
  Re: id() and is operator Chris Angelico <rosuav@gmail.com> - 2015-02-23 06:23 +1100
  Re: id() and is operator Gary Herron <gherron@digipen.edu> - 2015-02-22 11:16 -0800
  Re: id() and is operator Laura Creighton <lac@openend.se> - 2015-02-22 20:58 +0100
  Re: id() and is operator Marko Rauhamaa <marko@pacujo.net> - 2015-02-22 23:25 +0200
    Re: id() and is operator Chris Angelico <rosuav@gmail.com> - 2015-02-23 08:36 +1100
    Re: id() and is operator Terry Reedy <tjreedy@udel.edu> - 2015-02-23 01:02 -0500
      Re: id() and is operator Marko Rauhamaa <marko@pacujo.net> - 2015-02-23 08:31 +0200
    Re: id() and is operator Gary Herron <gherron@digipen.edu> - 2015-02-22 22:29 -0800
  Re: id() and is operator Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-23 12:31 +1100
  Re: id() and is operator Terry Reedy <tjreedy@udel.edu> - 2015-02-23 01:14 -0500

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