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Groups > comp.lang.python > #103874

Re: Explaining names vs variables in Python

Newsgroups comp.lang.python
Date 2016-03-02 07:08 -0800
References (3 earlier) <87y4a1t5wj.fsf@elektro.pacujo.net> <mailman.100.1456923030.20602.python-list@python.org> <87twkpt2w7.fsf@elektro.pacujo.net> <mailman.101.1456926519.20602.python-list@python.org> <87povdt1ec.fsf@elektro.pacujo.net>
Message-ID <fd538d95-4c3d-445f-a7dd-256545feff65@googlegroups.com> (permalink)
Subject Re: Explaining names vs variables in Python
From Rustom Mody <rustompmody@gmail.com>

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On Wednesday, March 2, 2016 at 7:42:09 PM UTC+5:30, Marko Rauhamaa wrote:
> Chris Angelico :
> 
> > On Thu, Mar 3, 2016 at 12:39 AM, Marko Rauhamaa  wrote:
> >> Chris Angelico :
> >>
> >>> Python defines that every object has an identity, which can be
> >>> represented as an integer. Since this is an intrinsic part of the
> >>> object, no two distinct objects can truly have identical
> >>> characteristics. Python's objects are like rifles - there are many
> >>> like it, but this one is mine.
> >>
> >> How can you be sure Python isn't returning the same id value for two
> >> distinct objects?
> >
> > The same way I can be sure about anything else in Python. It's a
> > language guarantee.
> 
> Actually, my question is (intentionally) nonsensical.
> 
> The sameness or distinctness of two objects is not directly defined in
> Python. The definition is simply:
> 
>    Two objects X and Y are called identical if
> 
>        X is Y
> 
>    evaluates to a true value.
> 
> Additionally, we have:
> 
>    If objects X and Y are identical, it is guaranteed that
> 
>       id(X) == id(Y)
> 
>    evaluates to a true value.
> 
> Even more strongly, we have:
> 
>    For any objects X and Y,
> 
>       id(X) == id(Y) if X is Y else id(X) != id(Y)
> 
>    evaluates to a true value.
> 
> What is missing is the rules that are obeyed by the "is" operator.

is is not is
is is was
[fermionic or bosonic?]

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Thread

Explaining  names  vs variables  in Python Salvatore DI DIO <salvatore.didio@gmail.com> - 2016-03-02 00:32 -0800
  Re: Explaining names vs variables in Python Jesper K Brogaard <jesper@brogAAaard.eu> - 2016-03-02 10:03 +0100
    Re: Explaining names vs variables in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-02 21:32 +1100
      Re: Explaining names vs variables in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-02 14:34 +0200
        Re: Explaining names vs variables in Python Chris Angelico <rosuav@gmail.com> - 2016-03-02 23:50 +1100
          Re: Explaining names vs variables in Python Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-02 15:11 +0200
          Re: Explaining names vs variables in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-02 15:39 +0200
            Re: Explaining names vs variables in Python Chris Angelico <rosuav@gmail.com> - 2016-03-03 00:48 +1100
              Re: Explaining names vs variables in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-02 16:11 +0200
                Re: Explaining names vs variables in Python Rustom Mody <rustompmody@gmail.com> - 2016-03-02 07:08 -0800
                Re: Explaining names vs variables in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-03 04:23 +1100
                Re: Explaining names vs variables in Python Rustom Mody <rustompmody@gmail.com> - 2016-03-02 09:28 -0800
                Re: Explaining names vs variables in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-02 20:12 +0200
                Re: Explaining names vs variables in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-03 12:52 +1100
                Re: Explaining names vs variables in Python Rustom Mody <rustompmody@gmail.com> - 2016-03-03 09:03 -0800
                Re: Explaining names vs variables in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-03 12:53 -0700
                Re: Explaining names vs variables in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-02 21:49 +0000
                Re: Explaining names vs variables in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-03 13:05 +1100
                Re: Explaining names vs variables in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-03 16:09 +0000
                Re: Explaining names vs variables in Python Chris Angelico <rosuav@gmail.com> - 2016-03-03 08:52 +1100
                Re: Explaining names vs variables in Python Rustom Mody <rustompmody@gmail.com> - 2016-03-02 17:23 -0800
                Re: Explaining names vs variables in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2016-03-02 22:51 +0000
              Re: Explaining names vs variables in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-03 04:10 +1100
  Re: Explaining names vs variables in Python Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2016-03-02 10:08 +0100
  Effects of caching frequently used objects, was Re: Explaining  names  vs variables  in Python Peter Otten <__peter__@web.de> - 2016-03-02 10:12 +0100
  Re: Explaining  names  vs variables  in Python Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-02 11:35 +0200
    Re: Explaining names vs variables in Python Ian Kelly <ian.g.kelly@gmail.com> - 2016-03-02 08:13 -0700
      Re: Explaining names vs variables in Python Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-03-02 17:37 +0200
  Re: Explaining  names  vs variables  in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-02 21:16 +1100
  Re: Explaining  names  vs variables  in Python "ast" <nomail@invalid.com> - 2016-03-02 11:52 +0100
    Re: Explaining  names  vs variables  in Python Salvatore DI DIO <salvatore.didio@gmail.com> - 2016-03-02 02:58 -0800
  Re: Effects of caching frequently used objects, was Re: Explaining  names  vs variables  in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-03-02 09:16 -0500
  Re: Explaining  names  vs variables  in Python Ben Finney <ben+python@benfinney.id.au> - 2016-03-03 04:53 +1100
  RE: Effects of caching frequently used objects, was Re: Explaining names  vs variables  in Python Albert-Jan Roskam <sjeik_appie@hotmail.com> - 2016-03-25 13:03 +0000
  Re: Effects of caching frequently used objects, was Re: Explaining names vs variables in Python Chris Angelico <rosuav@gmail.com> - 2016-03-26 00:22 +1100
  Re: Effects of caching frequently used objects, was Re: Explaining names  vs variables  in Python Ethan Furman <ethan@stoneleaf.us> - 2016-03-25 09:45 -0700

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