Frankly, I don't think an "as dict" protocol is worth it, but if others did think so, we could:
define a new dunder: __as_mapping__ (I'm using "mapping", rather than "dict", to allow duck typing) Then the built-in dict() constructor would: check for an __as_mapping__ dunder: -- if there, it would call it and expect to get a mapping back that it could turn into a dict. -- if not, it would go through its current process ( you could perhaps specify a subset of the mapping interface -- maybe all you'd need is .items(), for instance -- so it would actually return an iterator of key-value pairs. after all, dict() can already consume that.) Meanwhile, any other code that wants to could also use the __as_mapping__ dunder to be able to work with an object as though it were a mapping, even if that isn't its usual interface. As far as I can see, the only downside of this is that it would means a new standard dunder, which is a substantial downside, as (I think) it essentially adds overhead in all sorts of places, plus ads "One more protocol" to a language already ripe with protocols. At least that's the message I got when I suggested adding a dunder for a sorting key method. -CHB On Thu, May 9, 2019 at 10:13 AM Ricky Teachey <ri...@teachey.org> wrote: > Another difficulty I just thought of: > - a NT class- and a dcls, for that matter- could also be an iterable > two-tuples that would currently get dict-ified using iteration. So a > precedence rule- does iter() win? Or the asdict functions?- would be needed > for this, too. > > The answer to that seems a lot less obvious to me (compared to the mapping > protocol), since iterating k-v pairs is relying on a bit of a side effect, > but that side effect has probably existed since the dict was created. > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ > -- Christopher Barker, PhD Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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