[Numpy-discussion] comparing string array with None raises ValueError
jmiller at stsci.edu
Thu Jun 24 13:11:10 CDT 2004
On Thu, 2004-06-24 at 15:26, David M. Cooke wrote:
> On June 24, 2004 01:46 pm, Sebastian Haase wrote:
> > In general it must be OK to compare anything with None, right ?
> > (BTW, I get the same error with == and !=)
> No! Not in general!
Well, this is a good point. I think the current numerical behavior was
a hack I stuck in for people who might not be aware of "is". It's
looking like a mistake now.
> I learnt this back when Numeric implemented rich
> comparisions; suddenly, lots of my code broke. You don't actually want "is
> this object _equal_ (or not equal) to None", you want "is this object None",
> as None is a singleton.
However, given the context of the original question, Sebastian's code
doesn't read like *that* kind of None comparison:
> > > > type '10a80' - that is, an array of 10 80 char 'strings' :
> > > > >>> q.Mrc.hdr = q.Mrc.hdrArray.field
> > > > >>> q.Mrc.hdr('title') != None
q.Mrc.hdr('title') is pretty clearly a character array, ergo, it's not
None. What did you want it to do Sebastian?
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