adding an attribute to an nd-array

Stefan van der Walt stefan at sun.ac.za
Thu Oct 19 06:20:32 CDT 2006


On Wed, Oct 18, 2006 at 09:17:49PM -0400, Pierre GM wrote:
> On Wednesday 18 October 2006 20:29, Stefan van der Walt wrote:
> > A quick question on extending numpy arrays: is it possible to easily
> > add an attribute to an ndarray?
> 
> It might be easier to create a subclass: pleasehave a look here:
> http://projects.scipy.org/scipy/numpy/attachment/wiki/MaskedArray/test_subclasses.py
> That's a tiny example of subclassing ndarrays, with some extra attributes.
> (BTW, I'm not sure that's the most obvious place where to look: if it turns 
> out to be useful, I'll put it on the scipy wiki)

Thanks very much, Pierre.

If I understand correctly, the following should work:

import numpy as N

class InfoArray(N.ndarray):
    def __new__(info_arr_cls,arr,info={}):
        info_arr_cls.info = info
        return N.array(arr).view(info_arr_cls)

When does __array_finalize__ get called, and is it always necessary to
specify it?

Cheers
Stéfan

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