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To: python-list@python.org
From: Oscar Benjamin <oscar.j.benjamin@gmail.com>
Subject: Re: Using dict as object
Date: Wed, 19 Sep 2012 23:04:26 +0000 (UTC)
References: <345da32c-a22b-4025-bb50-794d684885b1@googlegroups.com> <5059B062.8020108@davea.name> <CAJ+soVegTjd_O-UYx8t400CFxXgd2B=ngt9JNzWJUVq+YNvXJA@mail.gmail.com>
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Xref: csiph.com comp.lang.python:29532

On 2012-09-19, Pierre Tardy <tardyp@gmail.com> wrote:
> --===============1362296571==
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>>
>>  This has been proposed and discussed and even implemented many
>> times on this list and others.
>>
> I can find this question on SO
> http://stackoverflow.com/questions/4984647/accessing-dict-keys-like-an-attribute-in-python
> which is basically answered with this solution
>
> class AttributeDict(dict):
>     __getattr__ = dict.__getitem__
>     __setattr__ = dict.__setitem__
>
>
> but this does not allow recursive access, you would need to first convert
> all nested dictionaries to AttributeDict.
> a.b.c.d = 2 # fail
> a.b = dict(c=3)
> a.b.c=4 # fail

There is no way to control "recursive access" in Python. The statement

a.b.c = 2

is equivalent to the statements

o = a.b   # o = a.__getattr__('b')
o.c = 2   # o.__setattr__('c', 2)

The way that the o.c assignment is handled is determined by the type of o
regardless of the type of a. If you're looking for a way to change only the
type of a and make a custom __(set|get)attr__ work for all dicts that are
indirectly referred to then there is no solution to your problem.

Oscar