I have often wanted this! I use defaultdict only occasionally, and every time I do, I start out thinking it behaves the way you describe dynamicdict. Then I read the docs again and decide I didn't actually want defaultdict to start with, and roll something different.
On Fri, Apr 10, 2020, 6:50 PM Steele Farnsworth <swfarnswo...@gmail.com> wrote: > I have implemented a class in the C code of the collections module which > has similar behavior to the defaultdict class. This class, dynamicdict, > supplies values for keys that have not yet been added using a default > factory callable, but unlike defaultdict, the missing key itself is passed > to the callable. This code can be seen here: > https://github.com/swfarnsworth/cpython/blob/3.8/Modules/_collectionsmodule.c#L2234 > > While this does introduce a lot of redundant code, I'm not sure how it > could be done without copying the implementation of the defaultdict class > and adjusting how the default factory is called. For example, I don't > believe that it's possible to support both behaviors within the defaultdict > class without breaking backwards compatibility or adding another parameter > to the constructor for the defaultdict class. > > I don't know if a PEP is needed for this to be added to the standard > library, or if it's something that anyone other than myself wants to see > added, but I would be happy to further explain the concept, implementation, > potential use cases, or anything else that might work towards the adoption > of this feature. > > Regards, > Steele > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/XYSY3K4O6AYSIIGOJGIO5XKNBHOM6B5S/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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