[Numpy-discussion] should numpy.equal raise an exception instead of returning NotImplemented?

Ernest Adrogué eadrogue@gmx....
Tue Jan 26 08:17:48 CST 2010


26/01/10 @ 08:59 (-0500), thus spake josef.pktd@gmail.com:
> 2010/1/26 Ernest Adrogué <eadrogue@gmx.net>:
> > Hi,
> >
> > Do you think it is sensible for np.equal to return a NotImplemented
> > object when is given an array of variable length dtype?
> > Consider this code:
> >
> > x = np.array(['xyz','zyx'])
> > np.where(np.equal(x, 'zyx'), [0,0], [1,1])
> >
> > the last line returns array([0, 0]) which is wrong. Compare with
> >
> > np.where(x == 'zyx', [0,0], [1,1])
> >
> > I think in this case raising an exception would be better, because
> > of the way np.equal is often used as an argument to another function.
> > It's not easy to see where the bug is or even that there is a bug
> > in your code.
> 
> there was a thread on this on december 7, but maybe nobody filed a ticket.

This ticket
http://projects.scipy.org/numpy/changeset/7878
seems to imply that now ufuncs raise an exception, so maybe it's
already been taken care of.

Thanks.

Ernest


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