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Re: Mutable objects inside tuples - good or bad?

References <89df32f9-c8ae-4b7b-bfc4-01c574aabcae@googlegroups.com> <53410185.6050304@islandtraining.com> <CABicbJK=Fw+m9pjgm9Ng=h=if38YL6uo4ibgiA43S6ohV9XUKg@mail.gmail.com> <CAPTjJmqkeWO8stSDGECcvyU2217uDeZgX9gtVC+0=58195sj=A@mail.gmail.com>
From Devin Jeanpierre <jeanpierreda@gmail.com>
Date 2014-04-06 04:01 -0700
Subject Re: Mutable objects inside tuples - good or bad?
Newsgroups comp.lang.python
Message-ID <mailman.8947.1396782118.18130.python-list@python.org> (permalink)

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On Sun, Apr 6, 2014 at 1:25 AM, Chris Angelico <rosuav@gmail.com> wrote:
> On Sun, Apr 6, 2014 at 5:55 PM, Devin Jeanpierre <jeanpierreda@gmail.com> wrote:
>> Agreed. Putting mutable objects inside tuples is common and totally OK.
>
> There are many programming habits that can cause problems, even though
> they won't break Python and are legal code. :)

Yes, but this isn't one of them.

>> c is such that you could have another variable d, where the following
>> interpreter session fragment is easily possible:
>>
>>>>> c == d
>> True
>>>>> foo(c)
>>>>> c == d
>> False
>
> What you're looking at here is hashability, not mutability. Compare:

No, that is not what I am looking at. There are hashable objects with
the property I described, and unhashable objects without it.

My point in that example was that sometimes it is more useful to talk
about entire objects and their behavior as a whole. Calling the object
"immutable" when it has mutable state is misleading in this context.

-- Devin

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Thread

Mutable objects inside tuples - good or bad? John Ladasky <john_ladasky@sbcglobal.net> - 2014-04-05 23:53 -0700
  Re: Mutable objects inside tuples - good or bad? Gary Herron <gary.herron@islandtraining.com> - 2014-04-06 00:25 -0700
  Re: Mutable objects inside tuples - good or bad? Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-04-06 00:55 -0700
    Re: Mutable objects inside tuples - good or bad? Rustom Mody <rustompmody@gmail.com> - 2014-04-06 08:07 -0700
  Re: Mutable objects inside tuples - good or bad? Chris Angelico <rosuav@gmail.com> - 2014-04-06 18:25 +1000
  Re: Mutable objects inside tuples - good or bad? Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-04-06 04:01 -0700
  Re: Mutable objects inside tuples - good or bad? Paul Kölle <paul@subsignal.org> - 2014-04-07 17:26 +0200
  Re: Mutable objects inside tuples - good or bad? Chris Angelico <rosuav@gmail.com> - 2014-04-08 01:44 +1000
  Re: Mutable objects inside tuples - good or bad? Paul Kölle <paul@subsignal.org> - 2014-04-07 21:46 +0200
  Re: Mutable objects inside tuples - good or bad? Chris Angelico <rosuav@gmail.com> - 2014-04-08 08:47 +1000
  Re: Mutable objects inside tuples - good or bad? Terry Reedy <tjreedy@udel.edu> - 2014-04-07 20:16 -0400
    Re: Mutable objects inside tuples - good or bad? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-08 02:53 +0000

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