[Numpy-discussion] Transforming an array of numbers to an array of formatted strings

[Alexander Michael]

Is there a better way than looping to perform the following transformation?

 import numpy
 int_data = numpy.arange(1,11, dtype=int) # just an example
 str_data = int_data.astype('S4')
 for i in xrange(len(int_data)):
... str_data[i] = 'S%03d' % int_data[i]

 print str_data
['S001' 'S002' 'S003' 'S004' 'S005' 'S006' 'S007' 'S008' 'S009' 'S010']

That is, I want to format an array of numbers as strings.

Thanks,
Alex
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Re: [Numpy-discussion] Transforming an array of numbers to an array of formatted strings

[Alan G Isaac]

On Thu, 13 Mar 2008, Alexander Michael apparently wrote:
 I want to format an array of numbers as strings. 

To what end?
Note that tofile has a format option.
And for 1d array ``x`` you can always do::

strdata = list( fmt%xi for xi in x)

Nice because the counter name does not bleed into your program.

Cheers,
Alan Isaac



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Re: [Numpy-discussion] Transforming an array of numbers to an array of formatted strings

[David Huard]

['S%03d'%i for i in int_data]

David


2008/3/13, Alan G Isaac [EMAIL PROTECTED]:

 On Thu, 13 Mar 2008, Alexander Michael apparently wrote:
  I want to format an array of numbers as strings.


 To what end?
 Note that tofile has a format option.
 And for 1d array ``x`` you can always do::

 strdata = list( fmt%xi for xi in x)

 Nice because the counter name does not bleed into your program.

 Cheers,
 Alan Isaac



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 Numpy-discussion@scipy.org
 http://projects.scipy.org/mailman/listinfo/numpy-discussion

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Re: [Numpy-discussion] Transforming an array of numbers to an array of formatted strings

[Alan G Isaac]

 2008/3/13, Alan G Isaac [EMAIL PROTECTED]:
 strdata = list( fmt%xi for xi in x)
 Nice because the counter name does not bleed into your program. 


On Thu, 13 Mar 2008, David Huard apparently wrote:
 ['S%03d'%i for i in int_data] 


The difference is that the counter bleeds
from the list comprehension.  I find that
obnoxious.

Cheers,
Alan Isaac



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Re: [Numpy-discussion] Transforming an array of numbers to an array of formatted strings

[Alexander Michael]

On Thu, Mar 13, 2008 at 9:49 AM, Alan G Isaac [EMAIL PROTECTED] wrote:
 And for 1d array ``x`` you can always do::

strdata = list( fmt%xi for xi in x)

 Nice because the counter name does not bleed into your program.

On Thu, Mar 13, 2008 at 3:07 PM, David Huard [EMAIL PROTECTED] wrote:
 ['S%03d'%i for i in int_data]

Thanks for the suggestions! I wasn't sure if there was a magic numpy
method to do the loop quickly (as the destination array is created
beforehand) without creating a temporary Python list, but I guess not.
The generator/list-comprehension is likely better than my prototype.

Regards,
Alex
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