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Re: Infinitely nested containers

References <931d12c0-12b3-4278-a9b9-1e2c32f138b3@googlegroups.com> <87bno16nsw.fsf@elektro.pacujo.net> <mailman.16114.1416591558.18130.python-list@python.org> <54701468$0$12986$c3e8da3$5496439d@news.astraweb.com>
Date 2014-11-22 15:50 +1100
Subject Re: Infinitely nested containers
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.16134.1416631815.18130.python-list@python.org> (permalink)

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On Sat, Nov 22, 2014 at 3:43 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> random832@fastmail.us wrote:
>
>> There's no reason not to allow it with tuples, but you can't do it.
>> Mainly because doing it in a single literal would require special
>> syntax, whereas you can simply append to a list a reference to itself.
>
> You can't append a list to itself in a single expression, you have to create
> the list first.

It's possible to have a list directly refer to itself:

lst = []
lst.append(lst)

It's not possible, with pure Python code, to create a tuple with a
reference to itself, because you have to create a tuple with a single
expression. Hence the comments about using the C API... and breaking
stuff.

ChrisA

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Thread

Infinitely nested containers Gill Shen <gillarete@gmail.com> - 2014-11-20 21:54 -0800
  Re: Infinitely nested containers Marko Rauhamaa <marko@pacujo.net> - 2014-11-21 09:00 +0200
    Re: Infinitely nested containers random832@fastmail.us - 2014-11-21 12:39 -0500
      Re: Infinitely nested containers Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-22 15:43 +1100
        Re: Infinitely nested containers Chris Angelico <rosuav@gmail.com> - 2014-11-22 15:50 +1100
          Re: Infinitely nested containers Rustom Mody <rustompmody@gmail.com> - 2014-11-21 21:02 -0800
            Re: Infinitely nested containers Chris Angelico <rosuav@gmail.com> - 2014-11-22 16:09 +1100
              Re: Infinitely nested containers Rustom Mody <rustompmody@gmail.com> - 2014-11-21 22:03 -0800
        Re: Infinitely nested containers Ethan Furman <ethan@stoneleaf.us> - 2014-11-22 11:50 -0800
          Re: Infinitely nested containers Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-23 16:59 +1100
            Re: Infinitely nested containers random832@fastmail.us - 2014-11-23 01:39 -0500
    Re: Infinitely nested containers Chris Angelico <rosuav@gmail.com> - 2014-11-22 04:47 +1100
    Re: Infinitely nested containers random832@fastmail.us - 2014-11-21 12:50 -0500
    Re: Infinitely nested containers Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 11:37 -0700
    Re: Infinitely nested containers Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-11-21 13:30 -0600
    Re: Infinitely nested containers Terry Reedy <tjreedy@udel.edu> - 2014-11-22 16:57 -0500
  Re: Infinitely nested containers Chris Angelico <rosuav@gmail.com> - 2014-11-21 18:03 +1100
  Re: Infinitely nested containers Ian Kelly <ian.g.kelly@gmail.com> - 2014-11-21 10:13 -0700

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