class OrderedDefaultDict, __missing__(), kwargs.pop('default_factory')
- Src:
https://gist.github.com/westurner/be22dba8110be099a35e#file-ordereddefaultdict-py
>From https://groups.google.com/d/msg/python-ideas/9bpR8-bNC6o/tQ92g7wLGAAJ :
On Fri, Oct 16, 2015 at 9:08 PM, Andrew Barnert via Python-ideas <
[email protected]> wrote:
> Actually, forget all that; it's even simpler.
>
> At least in recent 3.x, the only thing wrong with inheriting from both
> types, assuming you put OrderedDict first, is the __init__ signature. So:
>
> class OrderedDefaultDict(OrderedDict, defaultdict):
> def __init__(self, default_factory=None, *a, **kw):
> OrderedDict.__init__(self, *a, **kw)
> self.default_factory = default_factory
>
> More importantly, because __missing__ support is built into dict, despite
> the confusing docs for defaultdict, you don't really need defaultdict at
> all here:
>
> class OrderedDefaultDict(OrderedDict):
> def __init__(self, default_factory=None, *a, **kw):
> OrderedDict.__init__(self, *a, **kw)
> self.default_factory = default_factory
> def __missing__(self, key):
> self[key] = value = default_factory()
> return value
>
> And either of these should work with 2.5+ (according to
> https://docs.python.org/2/library/stdtypes.html#dict that's when
> dict.__missing__ was added).
>
...
This seems to keep a consistent __init__ signature with OrderedDict (by
> .pop()-ing 'default_factory' from kwargs instead of specifying as a
> positionalkwarg):
>
> class OrderedDefaultDict(OrderedDict):
> def __init__(self, *a, **kw):
> default_factory = kw.pop('default_factory', self.__class__)
> OrderedDict.__init__(self, *a, **kw)
> self.default_factory = default_factory
> def __missing__(self, key):
> self[key] = value = self.default_factory()
> return value
>
> I've added a few tests (as well as to_json, and _repr_json_
> https://gist.github.com/westurner/be22dba8110be099a35e/
> c1a3a7394e401d4742df0617900bde6ab2643300#file-ordereddefaultdict-py-L120-
> L122
> <https://www.google.com/url?q=https%3A%2F%2Fgist.github.com%2Fwesturner%2Fbe22dba8110be099a35e%2Fc1a3a7394e401d4742df0617900bde6ab2643300%23file-ordereddefaultdict-py-L120-L122&sa=D&sntz=1&usg=AFQjCNF8jH3Y4oHTVBCxhy0K2OPsRhj26g>
> (Without this fix,
> json.loads(output_json, object_pairs_hook=OrderedDefaultDict)
> doesn't seem to work).
On Thu, Mar 9, 2017 at 4:57 PM, Chris Barker <[email protected]> wrote:
>
>
> >If we really want to make defaultdict feel more "builtin" (and I don't see
>> >any reason to do so), I'd suggest adding a factory function:
>> >
>> >dict.defaultdict(int)
>>
>
>
>> Nice.
>>
>
> I agree -- what about:
>
> dict.sorteddict() ??
>
> make easy access to various built-in dict variations...
>
> -CHB
>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
> NOAA/NOS/OR&R (206) 526-6959 voice
> 7600 Sand Point Way NE (206) 526-6329 fax
> Seattle, WA 98115 (206) 526-6317 main reception
>
> [email protected]
>
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