[SciPy-dev] chararry array method

Christopher Hanley chanley at stsci.edu
Thu Dec 29 15:46:00 CST 2005



Travis Oliphant wrote:
> 
> I'm not sure.  Presumably it would pick up its shape from the input object.
> 
> At some point, I think I'd like to move the chararray into C and have it 
> be the default return object whenever a string or unicode base-type 
> array is requested.
> 
> You can already have arrays of strings without the chararray, except 
> comparisons don't work.  There are lots of ways to solve that problem, 
> and I'm not sure the chararray is the best way.  But, it's functional.
> 
> -Travis
> 

I guess I'm trying to understand if the following example will work.  In 
numarray, I can say the following:


In [24]: from numarray import strings as chararray

In [25]: arr2 = chararray.array('abcdefg'*10,itemsize=10)

In [26]: arr2
Out[26]:
CharArray(['abcdefgabc', 'defgabcdef', 'gabcdefgab', 'cdefgabcde',
            'fgabcdefga', 'bcdefgabcd', 'efgabcdefg'])

However, when attempting to do something similar with scipy.base I 
receive the following:

In [27]: arr = sb.chararray.array('abcdefg'*10,itemlen=10)
---------------------------------------------------------------------------
exceptions.ValueError                                Traceback (most 
recent call last)

/data/sparty1/dev/devCode/<console>

/data/sparty1/dev/site-packages/lib/python/scipy/base/chararray.py in 
array(obj, itemlen, copy, unicode, fortran)
     322     return chararray(val.shape, itemlen, unicode, buffer=val,
     323                      strides=val.strides,
--> 324                      fortran=fortran)
     325
     326 def asarray(obj, itemlen=7, unicode=False, fortran=False):

/data/sparty1/dev/site-packages/lib/python/scipy/base/chararray.py in 
__new__(subtype, shape, itemlen, unicode, buffer, offset, strides, fortran)
      28                                    buffer=buffer,
      29                                    offset=offset, strides=strides,
---> 30                                    fortran=fortran)
      31         return self
      32

ValueError: need to give a valid shape as the first argument

Chris




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