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Groups > comp.lang.python > #29569

Re: looping in array vs looping in a dic

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On Thu, Sep 20, 2012 at 1:09 PM, MRAB <python@mrabarnett.plus.com> wrote:
> for col in range(cols):
>     for row in range(rows):
>         cat = valuesCategory[row, col]
>         ras = valuesRaster[row, col]
>         totals[cat] += ras

Expanding on what MRAB wrote, since you probably have far fewer
categories than pixels, you may be able to take better advantage of
numpy's vectorized operations (which are pretty much the whole point
of using numpy in the first place) by looping over the categories
instead:

for cat in categories:
    totals[cat] += np.sum(valuesCategory * (valuesRaster == cat))

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looping in array vs looping in a dic giuseppe.amatulli@gmail.com - 2012-09-20 11:31 -0700
  Re: looping in array vs looping in a dic MRAB <python@mrabarnett.plus.com> - 2012-09-20 20:09 +0100
  Re: looping in array vs looping in a dic Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-20 13:28 -0600
  Re: looping in array vs looping in a dic Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-20 13:29 -0600
    Re: looping in array vs looping in a dic giuseppe.amatulli@gmail.com - 2012-09-20 16:35 -0700
      Re: looping in array vs looping in a dic MRAB <python@mrabarnett.plus.com> - 2012-09-21 00:58 +0100
    Re: looping in array vs looping in a dic giuseppe.amatulli@gmail.com - 2012-09-20 16:35 -0700

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