The meaning of "="

Piet van Oostrum piet at cs.uu.nl
Mon Jul 13 14:15:07 CEST 2009


>>>>> Lawrence D'Oliveiro <ldo at geek-central.gen.new_zealand> (LD) wrote:

>LD> In message <h3bogf$oo0$1 at panix3.panix.com>, Aahz wrote:

>Aahz> class AttrDict:
>Aahz> def __getitem__(self, key):
>Aahz> return getattr(self, key)

>LD> OK, let's try it:

>LD> >>> c = {}
>LD> >>> c["x"] = 3
>LD> >>> c.x = 4   
>LD>     Traceback (most recent call last):
>LD>       File "<stdin>", line 1, in <module>
>LD>     AttributeError: 'dict' object has no attribute 'x'
>LD> >>> class AttrDict:
>LD>     ...     def __getitem__(self, key):
>LD>     ...         return getattr(self, key)
>LD>     ...
>LD> >>> c.x = 4
>LD>     Traceback (most recent call last):
>LD>       File "<stdin>", line 1, in <module>
>LD>     AttributeError: 'dict' object has no attribute 'x'

>LD> Nope, still doesn't work...

Of course you need c = AttrDict()

And to get c.x = 4 working you also need a __setitem__. 
And to get c["x"] working AtrrDict should subclass dict:

>>> class AttrDict(dict):

but these are only minor details :=)
-- 
Piet van Oostrum <piet at cs.uu.nl>
URL: http://pietvanoostrum.com [PGP 8DAE142BE17999C4]
Private email: piet at vanoostrum.org



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