Infinitely nested containers

Chris Angelico rosuav at gmail.com
Sat Nov 22 05:50:12 CET 2014


On Sat, Nov 22, 2014 at 3:43 PM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> random832 at 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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