Naive Question

[jim kraai]

Michael Hudson wrote:
> 
> jim kraai <jkraai at murl.com> writes:
> 
> > Greetings,
> >
> > If I have:
> >
> > class contrived_collection:
> >       def __init__(self):
> >               self.item = [{1,2},{3,4},{5,6}]
> >
> > a = contrived_collection()
> > b = a.item[2]
> >
> > How can I ask b what it is a member of?
> 
> You can't, at least not without basically adding the information
> yourself. Watch out for cycles!

That's what I was afraid of.

> > I need to somehow know later in processing that:
> > 1. b is a member of a.item
> > 2. a.item is a member of a
> 
> Hmm... what are you trying to do? Have you looked at Acquisition:

I want to make a recursive directory'ish listing and have a list 
of indexes into it.

Now, I believe that I'll do it backwards.  Have a linear list of 
directory objects, and have a nested list of refs to them.  Doesn't 
solve the problem in the way that I wanted to do it, but thats OK!
Thanks!

> http://www.zope.org/Members/Amos/WhatIsAcquisition
> 
> (which is zope biased; there may be another more generic intro
> somewhere but I can't find it just now).
> 
> It s a very cute method for dealing with some problems a bit like
> this.

Hm, I've been able to avoid the Alternate Zope Universe to date.

Thanks for the answer to the question!

--jim