"indexed properties"...

[castironpi]

On May 20, 10:40 am, "David C. Ullrich" <dullr... at sprynet.com> wrote:
> In article <20080520154802.4b5df647 at hyperspace>,
>
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>
>
>
>  pataphor <patap... at gmail.com> wrote:
> > On Tue, 20 May 2008 06:12:01 -0500
> > David C. Ullrich <dullr... at sprynet.com> wrote:
>
> > > Well, ok. Like I said, I never _took_ the position that it _should_
> > > be a list of lists, I just said I didn't see the advantage to using
> > > a single list.
>
> > I'm now thinking about a list of lists containing single element lists.
>
> > def test():
> >     n = 3
> >     R = range(n)
> >     M = [[[i+j*n] for i in R] for j in R]
> >     for L in M:
> >         print L
> >     row2 = M[1]
> >     print
> >     print row2
> >     col3 = [L[2] for L in M]
> >     print col3
> >     col3[1][0]=9
>
> > print col3
> >     print row2
> >     print
> >     for L in M:
> >         print L
>
> > if __name__=='__main__':
> >         test()
>
> > The idea is to use a single element list as kind of storage facility.
> > That enables me to copy a column, then change something in that column
> > and make the change turn up in the matrix and even in a previously made
> > copy of a row that shared the specific element.
>
> > > Today's little joke: Long ago I would have solved
> > > this by storing the data as a list of rows and _also_
> > > a list of columns, updating each one any time the
> > > other changed. Just goes to show you things
> > > could always be worse...
>
> > Well have I ever ... I only thought about this last week and I
> > actually thought it was a *good* idea.
>
> Sorry. If you really want to do this you could keep things
> in sync automatically by writing the appropriate __setitem__
> and resolving never to modify the data except through that...
>
> def whatever.__setitem__(self, (row,col), value):
>   self.rows[row][col] = value
>   self.cols[col][row] = value
>
> Seems to me like an, um, "untenable" waste of space. And you'd
> need to be certain to never set anything except through
> self[row,col]; as far as I can see anything like setrow()
> would be a loop "for col in range(width): self[row,col] =".
>
> Hmm. You could keep the data in some object that encapsulates
> the two double lists and use some fancy feature (__getattribute__?)
> to make certain that the only possible access to the data
> was through __getitem__...
>
>
>
>
>
> > I only gave up on it because
> > now I would have to keep  track of how far the two views are out of
> > sync, because some operation could use data that was modified by an
> > other view. Zipstar transposition is very handy for syncing, but it is
> > also very expensive. But probably not for you.
>
> > > Expressing interest is a big mistake...
>
> > How so? ;-)
>
> > > Sometime soon a thread will appear titled something
> > > like "indexed attributes" with a stripped-down but
> > > functional example of what I have in mind for Matrix
>
> > I can't wait! Keep up the good work.
>
> > P.
>
> --
> David C. Ullrich- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

You can use tuples in dictionaries.

Example:

>>> a= {}
>>> a[0,1]= 2
>>> a[2,3]= 7
>>> a[0,1]
2