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Re: Explaining names vs variables in Python

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Steven D'Aprano <steve@pearwood.info>:

> On Wed, 2 Mar 2016 08:03 pm, Jesper K Brogaard wrote:
>
>> As I understand it, when you use 'is', you are comparing addresses to
>> objects, not the values contained in the objects. Use '==' instead.
>
> You should not think about addresses, because the location of objects
> is not part of the language. It is implementation-dependent.

The ontological question is, can two *distinct* objects with *identical*
characteristics exist?

The fermionic answer is, no.

The bosonic answer is, sure.

Set theory has fermionic ontology (it's called extensionality).

Python sits on the fence on that one, allowing either ontology.

> This is why the id() function is NOT documented as returning the
> address of an object, but of returning an ID number. Let's look at IDs
> in IronPython:
>
>>>> a, b, c = [], 10000, "Hello world!"
>>>> print id(a), id(b), id(c), id(None)
> 43 44 45 0
>
>
> And in Jython:
>
>>>> a, b, c = [], 10000, "Hello world!"
>>>> print id(a), id(b), id(c), id(None)
> 1 2 3 4

Python doesn't define or use the concept of an "address."


Marko

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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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