[Numpy-discussion] ndarray: subclassing a subclass looses custom attribute

[Pierre GM]

On Oct 1, 2010, at 11:26 AM, Sebastian Haase wrote:

> Hi,
> I'm trying to add a 'meta' attribute to ndarray to keep track of image
> data filenames and resolution etc.
> Following  the excellent document
> http://docs.scipy.org/doc/numpy/user/basics.subclassing.html
> this worked right away.
> 
> However, I had done this before for some specific image-file-types:
> those would add there own attribute to ndarray array (e.g. arr.Mrc)
> Now if I call the new  ndarray_meta on my ndarray_with_mrc I loose the
> `Mrc` attribute, leaving only the new `meta` attribute.
> My code is essentially a verbatim copy of
> http://docs.scipy.org/doc/numpy/user/basics.subclassing.html#simple-example-adding-an-extra-attribute-to-ndarray
> 
> What can I do ?

Post your code, so that we can see what you actually did.

If I had to guess, I'd say you forgot to define your 'Mrc' attribute in your ndarray_meta.__array_finalize__. But once again, without some code, it's only a guess.