[Python-Dev] PEP 455: TransformDict (original) (raw)

Russell E. Owen rowen at uw.edu
Mon Oct 7 22:01:36 CEST 2013

In article <C4C036B6-130C-4718-BEB1-A7C9230082F4 at gmail.com>, Raymond Hettinger <raymond.hettinger at gmail.com> wrote:

On Sep 22, 2013, at 6:16 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> Are we close to asking for pronouncement? When you're ready, let me know. In the meantime, I conducting usability tests on students in Python classes and researching how well it substitutes for existing solutions for case insensitive dictionaries (the primary use case) and for other existing cases such as dictionaries with unicode normalized keys. If you want to participate in the research, I could also use help looking at what other languages do. Python is not the first language with mappings or to encounter use cases for transforming keys prior to insertion and lookup. I would like to find out what work has already been done on this problem. Another consideration is whether the problem is more general that just dictionaries. Would you want similar functionality in all mapping-like objects (i.e. a persistent dictionaries, os.environ, etc)? Would you want similar functionality for other services (i.e. case-insensitive filenames or other homomorphisms). You can also add to the discussion by trying out your own usability tests on people who haven't been exposed to this thread or the pep. My early results indicate that the API still needs work. ... * Another issue is that we're accumulating too many dictionary variants and that is making it difficult to differentiate and choose between them. I haven't found anyone (even in advanced classes with very experienced pythonistas) would knew about all the variations: dict, defaultdict, Mapping, MutableMapping, mapping views, OrderedDict, Counter, ChainMap, andTransformDict.

I agree.

I personally think being able to transform keys would be much more useful as a property of existing dictionaries. I often use case-insensitive keys. But I use them with dict and OrderedDict (and probably ought to use defaultdict, as well).

TransformDict is neat, but I'd personally be happier seeing this as a 3rd party library for now.

-- Russell

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