which "dictionary with attribute-style access"?

baloan baloand at googlemail.com
Thu Oct 22 09:30:05 CEST 2009


On Oct 22, 6:34 am, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
wrote:
> > class AttrDict(dict):
> >      """A dict whose items can also be accessed as member variables."""
> >      def __init__(self, *args, **kwargs):
> >          dict.__init__(self, *args, **kwargs)
> >          self.__dict__ = self
>
> >      def copy(self):
> >          return AttrDict(self)
>
> >      def __repr__(self):
> >          return 'AttrDict(' + dict.__repr__(self) + ')'
>
> >      @classmethod
> >      def fromkeys(self, seq, value = None):
> >          return AttrDict(dict.fromkeys(seq, value))
>
> Looks fine as long as nobody uses an existing method name as adictionary 
> key:
>
> py> d = AttrDict({'name':'value'})
> py> d.items()
> [('name', 'value')]
> py> d = AttrDict({'items': [1,2,3]})
> py> d.items()
> Traceback (most recent call last):
>    File "<stdin>", line 1, in <module>
> TypeError: 'list' object is not callable
>
> (I should have included a test case for this issue too).
> Of course, if this doesn't matter in your application, go ahead and use  
> it. Just be aware of the problem.
>
> --
> Gabriel Genellina

I see two ways to avoid collisions with existing method names:

1. (easy, reduced functionality) override __setattr__ and __init__,
test for keys matching existing method names, throw an exception if
exists (KeyError).
2. (complex, emulates dict) override __setattr__ and __init__, test
for keys matching existing method names, and store those keys in a
shadow dict. More problems arise when thinking about how to choose
access between dict method names and item keys.

--
Andreas Balogh
baloand at gmail dot com



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