[AstroPy] modifying FITS data

[Erik Bray]

On 05/31/2011 12:01 PM, Frédéric Grollier wrote:
> On Tue, May 31, 2011 at 04:53:55PM +0200, Jean-Luc Menut wrote:
>> Hello All,
>
> [snip]
>
>> What I would like to do is to replace these value by some others
>> (actually interpolated from other FITS data).
>>
>> By example, if I try to do
>>
>> In [80]: orig['OI_VIS'].data['VISAMP']=tuple(ones(14))
>>
>> I obtain:
>> ValueError: field named VISAMP not found.
>
> Hello,
>
> doing this with a loop should work:
>
> for i in range(orig['OS_VIS'].data.shape[0]):
>      orig['OI_VIS'].data.field('VISAMP')[i] = the_value
>
>

Rather than looping it might be better (certainly faster) to do a slice 
assignment:

orig['OI_VIS'].data['VISAMP'][:] = the_value

If the_value is not the same size/dimensions as the array being assigned 
to, then you can modify the slice accordingly.  For example:

orig['OI_VIS'].data['VISAMP'][:len(the_value)] = the_value

This works because the lookup by field name returns a numpy array that 
can be manipulated as such.  Why direct assignment like you tried 
originally isn't implemented I'm not entirely sure.

Erik