[Python-ideas] Revisiting Immutable Mappings

Chris Angelico rosuav at gmail.com
Tue Oct 16 05:26:52 EDT 2018

On Tue, Oct 16, 2018 at 7:02 PM George Leslie-Waksman <waksman at gmail.com> wrote:
> Would a frozendict require that keys and values be hashable?

Keys would already have to be hashable - regular dicts demand this,
and there's no reason not to for frozendict.

Values? Not so sure. Personally I would say that no, they don't HAVE
to be hashable - but that the frozendict itself would then not be

> It seems to me that we would need this restriction to make a reasonably universal frozendict that is, itself, hashable.

The tuple provides a good precedent here:

>>> hash((1,2,3))
>>> hash((1,2,[]))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'


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