[Python-Dev] Dict access with double-dot (syntactic sugar)

[Bob Ippolito]

On Thu, Mar 24, 2011 at 11:46 AM, Jameson Quinn <jameson.quinn at gmail.com> wrote:
>>
>> If you need this for **kw arguments maybe you're not using them right;
>> why not name your arguments if you're going to reference them by name?
>
> Good point.
>>
>> The JSON use case seems to be driven because this is the way
>> JavaScript does things -- they don't distinguish between dicts and
>> objects. I personally think that's a poor language feature: it blurs a
>> line that should be clear, between data (dict keys) and program
>> variables (attributes).
>>
> OK. So if this is a json-only issue, it can be done using a wrapper and
> object_hook in the json library. I believe that, since all the magic
> functions are pulled from the class, not the instance, you should even be
> able to use  "if 'a' in wrapped_dict:" and "for a in wrapped_dict:" if your
> wrapper class delegates __contains__ and __iter__ to the underlying dict.
> Anyway, you can use hasattr for the former.
> So my overarching proposal has shrunk to a suggestion that I should go and
> make a attrlyjson module which does this by default. I certainly think that
> I can get it right, and I know that there are several easy ways to get it
> wrong, so it's worth saving people the headache.

You're correct, this is trivial with object_hook.

>>> class AttrDict(dict):
...     def __getattr__(self, attr):
...         try:
...             return self[attr]
...         except KeyError:
...             raise AttributeError(attr)
...
>>> import json
>>> obj = json.loads('{"foo": {"bar": "baz"}}', object_hook=AttrDict)
{u'foo': {u'bar': u'baz'}}
>>> obj.foo.bar
u'baz'

-bob