[Numpy-discussion] recarray field names

Travis Oliphant oliphant at ee.byu.edu
Wed Mar 15 16:02:01 CST 2006

Erin Sheldon wrote:

>On 3/15/06, Perry Greenfield <perry at stsci.edu> wrote:
>>You are right that this is messy. We would like to change this
>>sometime. But we'd like to complete the transition to numpy first
>>before doing that so it may be some months before we can (and it may
>>not look quite like what you suggest). But your point is very valid.
>>Thanks, Perry
>OK, fair enough.
>Incidentally, I realized  that this attribute
>_coldefs is not part of recarray anyway, but something added by pyfits.
>I see now that the names and the formats with a greater than sign
>concatenated on the front can be extracted from dtype:
>In [247]: t.dtype
>Out[247]: [('x', '>f4'), ('y', '>i4')]
>I could write my own function to extract what I need, but I thought I
>would ask: is there already a simpler way?  And is there a function to
>compare this '>f4' stuff to the named types such as Float32 ('f')?

The dtype object does contain what you want.  In fact.  It's the fields 
attribute of the dtype object that is a dictionary accessed by field 
name.  Thus, to see if a field is a valid field itdentifier,

if name in t.dtype.fields:

would work  (well there is a slight problem in that -1 is a special key 
to the dictionary that returns a list of field names ordered by offset 
and so would work also), but if you now that name is already a string, 
then no problem.


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