[Python-ideas] Revisiting Immutable Mappings

Michael Selik mike at selik.org
Wed Oct 10 15:36:33 EDT 2018

How does a frozendict help in that example? It's not obvious to me.

Despite not understanding that example, I'm +1 for having a frozendict. I
don't think it'll increase cognitive load much, as it'll sit right next to
frozenset when someone reads the builtins in alphabetical order. In my own
experience, I want to use a dict as a dict key about once or twice a year.
It'd be nice to have a quick way to convert to a frozendict.

On Wed, Oct 10, 2018 at 10:05 AM Philip Martin <philip.martin2007 at gmail.com>

> Hi, I first want to thank everyone in the community for the contributions
> over the years. I know the idea of a frozendict has been proposed before
> and rejected. I have a use case for a frozendict implementation that to my
> knowledge was not discussed during previous debates. My reasoning for a
> frozendict class stems from patterns I typically see arise when performing
> ETL or data integrations and conversions. I generally have used
> MappingProxyType as a way to set default mapping to a function or to set an
> empty mapping to a function. I've created a gist with an example use case:
> https://gist.github.com/pmart123/493edf84d9aa61691ca7321325ebb6ab
> I've included an example of what code typically looks like when using
> MappingProxyType and what it could look like with a
> frozendict implementation. I believe this use case may also be
> under-reported in open source code as it often crops up when integrating
> third-party data sources, which at times can't be open sourced due to
> licensing issues. I would love to hear if anyone has used MappingProxyType
> in a similar manner, or if this use case could help warrant a frozendict in
> the standard library.
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