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

[Robert K. <rob...@gm...>]

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.

One certainly could write a subclass of array that handles arbitrarily-based
indices. On the other hand, writing a correct and consistent implementation
would be very tricky. On the gripping hand, a quick hack might suffice if one
only needed to use it locally, like inside a single function, and convert to and
from real arrays at the boundaries.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco