[Numpy-discussion] Usage of numpy.where and pylab.find with strings

Ariel Rokem arokem@berkeley....
Mon Jan 26 17:18:42 CST 2009


Doh! That's embarrassing!
Thanks!

On Jan 26, 2009, at 12:00 PM, Keith Goodman wrote:

> On Mon, Jan 26, 2009 at 11:48 AM, Ariel Rokem <arokem@berkeley.edu>  
> wrote:
>> Hi - I am trying to find a string in a list with strings and have  
>> come
>> across the following state of affairs:
>> In [228]: subjects
>> Out[228]:
>> ['KAA',
>> 'CCS',
>> 'EJS',
>> 'MNM',
>> 'JHS',
>> 'LJL',
>> 'DVA',
>> 'FCL',
>> 'CNC',
>> 'KFM',
>> 'APM',
>> 'GMC']
>> In [229]: subjects[0]
>> Out[229]: 'KAA'
>> In [230]: subjects[0] == 'KAA'
>> Out[230]: True
>> In [231]: np.where(subjects == 'KAA')
>> Out[231]: ()
>> In [232]: pylab.find(subjects == 'KAA')
>> Out[232]: array([], dtype=int32)
>> It doesn't seem to matter if I make the list into an array:
>> In [233]: np.array(subjects)
>> Out[233]:
>> array(['KAA', 'CCS', 'EJS', 'MNM', 'JHS', 'LJL', 'DVA', 'FCL', 'CNC',
>>       'KFM', 'APM', 'GMC'],
>>      dtype='|S3')
>> In [234]: pylab.find(subjects == 'KAA')
>> Out[234]: array([], dtype=int32)
>> In [235]: np.where(subjects == 'KAA')
>> Out[235]: ()
>> What am I doing wrong? What does it mean that the dtype is IS3?
>
> I think you made a typo. Try changing line 233 to subjects =  
> np.array(subjects)
>
>>> type(subjects)
>   <type 'list'>
>>> np.where(subjects == 'KAA')
>   ()
>>> np.where(np.asarray(subjects) == 'KAA')
>   (array([0]),)
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