New submission from Steele Farnsworth :
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 would be happy to further explain the concept, implementation, potential use
cases, or anything else that might work towards the adoption of this feature.
--
components: ctypes
messages: 366157
nosy: Steele Farnsworth
priority: normal
severity: normal
status: open
title: Proposed class for collections: dynamicdict
type: enhancement
versions: Python 3.9
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<https://bugs.python.org/issue40248>
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