[Numpy-discussion] comparing string array with None raises ValueError

Todd Miller jmiller at stsci.edu
Thu Jun 24 11:47:02 CDT 2004


On Thu, 2004-06-24 at 13:46, Sebastian Haase wrote:
> On Thursday 24 June 2004 10:31 am, Todd Miller wrote:
> > On Thu, 2004-06-24 at 13:06, Sebastian Haase wrote:
> > > Hi,
> > > I'm not sure if this is fixed already in CVS but here it goes:
> > > I'm working with record arrays, and trying to access a field with
> > >
> > > type '10a80' - that is, an array of 10 80 char 'strings' :
> > > >>> q.Mrc.hdr = q.Mrc.hdrArray[0].field
> > > >>> q.Mrc.hdr('title') != None
> >
> > Shouldn't this be:
> >
> > q.Mrc.hdr('title') != ""
> 
> (in my first reply, I forgot to point out that q.Mrc.hdr('title') is an ARRAY 
> of strings ! )
> 
> No, I understand that this makes more sense, but I have some "display 
> hook"-code that compares everything with None...
> In general it must be OK to compare anything with None, right ?
> (BTW, I get the same error with == and !=)

OK,  I see your point.  I talked it over with Perry and he made a
reasonable case for allowing comparisons with None (or any object). 
Perry argued that since None is a common default parameter value, it
might simplify code to not have to add logic to handle that case. 

If no one objects,  I'll change numarray.strings so that comparison of a
string array with any object not convertible to a string array results
in an array of False values.

Any objections?

Regards,
Todd







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