[Tutor] Descriptors api doubt

[Wesley Chun]

On Tue, 15 Jan 2002, Karthik Gurumurthy wrote:
>
> quoting from ,
> http://www.amk.ca/python/2.2/index.html#SECTION000320000000000000000
>
> For example, when you write obj.x, the steps that Python actually perform=
s
> are:
>
> descriptor =3D obj.__class__.x
> descriptor.__get__(obj)
>
> This is what i did:
>
> class test(object):
> =09def __init__(self):
> =09=09self.name =3D "python"
>
> >>> t =3D test()
> >>> desc =3D t.__class__.name
> Traceback (most recent call last):
>   File "<pyshell#15>", line 1, in ?
>     ob =3D t.__class__.name
> AttributeError: type object 'test' has no attribute 'name'
>
> if python does that internally, then why am in not able to access the
> descriptor
> corresponding to "name". is it named something different?
>
> The article says the descriptors live inside clas objects.
> Does that mean they are static members ? or is something totally differen=
t?


good Python 2.2 question.  i could be mistaken, but from what
i have read so far, i think that descriptors are only used/
useful for *class* attributes.  you were messing with an
*instance* attribute.  a class attribute is either a static
data member or a method.

i haven't checked the source to see how they have been imple-
mented in the code though.  hopefully someone else can chip in
there.

hope this helps a little!

-wesley

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"Core Python Programming", Prentice Hall PTR, =A9 2001
    http://starship.python.net/crew/wesc/cpp/

    wesley.j.chun :: wesc@deirdre.org
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