[SciPy-User] Padded data structure

Warren Weckesser warren.weckesser@enthought....
Sun Feb 21 09:05:59 CST 2010


Miguel de Val Borro wrote:
> On Sun, Feb 21, 2010 at 02:02:09AM -0600, Warren Weckesser wrote:
>   
>> Miguel de Val Borro wrote:
>>     
>>> On Sat, Feb 20, 2010 at 10:55:59PM -0800, Christopher Barker wrote:
>>>       
>>>>> I would like to read padded output files from C structures that look
>>>>> like this file:
>>>>> http://spec.jpl.nasa.gov/ftp/pub/catalog/catdir.cat The second
>>>>> row is a 13 character string that contains whitespaces.  I
>>>>> have looked at the align option in dtype passed as a parameter to
>>>>> loadtxt but could not make it work.
>>>>>           
>>>> Since there is whitespace between all those columns, I don't
>>>> think you need align.  I suspect that a dtype something like:
>>>>
>>>> ('i4', 'S13', 'i4', 'f8', 'f8','f8','f8','f8','f8','f8', 'i2')
>>>>         
>>> The problem is that the S13 string contains whitespaces, which is also
>>> the separator between columns. Using this dtype I get the error:
>>>
>>> ValueError: invalid literal for float(): v2,2v2,v
>>>
>>>       
>> Any chance you can upgrade your numpy version to the current trunk?
>> Somewhere between version 1.3.0 and the current trunk, the
>> 'delimiter' argument of genfromtxt() was enhanced to accept a list
>> of field widths.  The attached script shows how it can be used to
>> read the file "catdir.dat".
>>     
>
> Thank you very much for the script, it does exactly what I needed.
> Actually genfromtxt accepts field widths also in numpy 1.3.0 shipped
>   

Well, that's a nice surprise.  It works for me too in 1.3.0.  This 
feature is not mentioned in the docstring in 1.3.0, so I didn't think to 
try it.

Cheers,

Warren


> with Ubuntu 9.10. It looks like the function is not easy to find in the
> documentation, althought this may be already fixed in the repository.
>
> Miguel
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