[Numpy-discussion] Masked array fill_value

[Pierre GM]

On Saturday 19 July 2008 18:41:22 Ryan May wrote:
> > There was a thread about this a couple months ago, and Pierre GM
> > explained it.  I think the point was that indexing is giving you a new
> > masked scalar, which is therefore taking the default mask value of the
> > type.  I don't see it as a problem; you can always specify the fill
> > value explicitly when you need to.

Actually, in that example, a[2] is THE masked scalar: that's a constant 
initialized when you import numpy.ma, it doesn't depend on the type.

> I thought it sounded familiar.  You're right, it's not a big problem, it
> just seemed unintuitive.  Thanks for the explaination.

It is in a way, but it's needed for compatibility with older code. That way, 
you can test whether a value is masked by using:
a[2] is masked

Yeah, you could also check whether the mask if not nomask and whether the mask 
at this particular element is True, but it's a bit longer.