[Numpy-discussion] np.sign and object comparisons

[Sebastian Berg]

On Mo, 2015-08-31 at 10:23 -0700, Stephan Hoyer wrote:
> On Mon, Aug 31, 2015 at 1:23 AM, Sebastian Berg
> <sebastian at sipsolutions.net> wrote:
>         That would be my gut feeling as well. Returning `NaN` could
>         also make
>         
>         sense, but I guess we run into problems since we do not know
>         the input
>         type. So `None` seems like the only option here I can think of
>         right
>         now.
> 
> 
> My inclination is that return NaN would be the appropriate choice.
> It's certainly consistent with the behavior for float dtypes -- my
> expectation for object dtype behavior is that it works exactly like
> applying the np.sign ufunc to each element of the array individually.
> 

I was wondering a bit if returning the original object could make sense.
It would work for NaN (and also decimal versions of NaN, etc.). But I am
not sure in general.

- Sebastian

> 
> On the other hand, I suppose there are other ways in which an object
> can fail all those comparisons (e.g., NaT?), so I suppose we could
> return None. But it would still be a weird outcome for the most common
> case. Ideally, I suppose, np.sign would return an array with int-NA
> dtype, but that's a whole different can of worms...
> 
> 
> Stephan
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