[Numpy-discussion] arrays that start from negative numbers?

[Rick Muller]

I certainly think that something along these lines would be possible.  
However, in the end I just decided to keep track of the indices using  
a Python dictionary, which means to access A[-3] I actually have to  
call A[index[-3]]. A little clunkier, but I was worried that the  
other solutions would be brittle in the long run.

Thanks for all of the comments.

On May 30, 2006, at 2:04 PM, David Huard wrote:

> Just a thought:
> would it be possible to overload the array __getitem__ method ?
>
> I can do it with lists, but not with arrays...
>
> For instance,
>
> class fortarray(list):
>     def __getitem__(self, index):
>         return list.__getitem__(self, index+5)
>
> and
> >>> l = fortarray()
> >>> l.append(1)
> >>> l[-5]
> 1
>
> There is certainly a more elegant way to define the class with the  
> starting index as an argument, but I didn't look into it. For  
> arrays, this doesn't work out of the box, but I'd surprised if  
> there was no way to tweak it to do the same.
>
> Good luck
> David
>
> 2006/5/30, Rick Muller <rmuller at sandia.gov>:
> Indeed I am. Thanks for the reply
> On May 30, 2006, at 11:32 AM, Rob Hetland wrote:
>
> >
> > I believe Rick is talking about negative indices (possible in
> > FORTRAN), in which case the answer is no.
> >
> > -Rob
> >
> > On May 30, 2006, at 11:28 AM, Rick Muller wrote:
> >
> >> Is it possible to create arrays that run from, say -5:5, rather
> >> than 0:11? Analogous to the Fortran "allocate(A(-5:5))" command?
> >> I'm translating a F90 code to Python, and it would be easier to do
> >> this than to use a python dictionary.
> >
> > -----
> > Rob Hetland, Assistant Professor
> > Dept of Oceanography, Texas A&M University
> > p: 979-458-0096, f: 979-845-6331
> > e: hetland at tamu.edu, w: http://pong.tamu.edu
> >
> >
>
> Rick Muller
> rmuller at sandia.gov
>
>
>
>
>
>
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Rick Muller
rmuller at sandia.gov



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