[GRASS-dev] Parsing output of r.category which includes labels

Stefan Blumentrath Stefan.Blumentrath at nina.no
Mon Aug 20 03:48:34 PDT 2018

Hi Nikos,

You could use numpy and genfromtxt() to parse the output string...
genfromtxt() requires an StringIO object (or file) and StringIO (from io) requires unicode()...

So you could do:

from io import StringIO
import numpy as np
output = np.genfromtxt(StringIO(unicode(grass.read_command('r.category', map=base))) , delimiter='\t', dtype=None, names=['cat', 'label'])

That causes however some overhead [1]. So if it makes sense depends on what you want to do with the data in the further processing chain...


1: https://docs.scipy.org/doc/numpy/user/basics.io.genfromtxt.html

-----Original Message-----
From: grass-dev <grass-dev-bounces at lists.osgeo.org> On Behalf Of Nikos Alexandris
Sent: s√łndag 19. august 2018 22:19
To: GRASS-GIS development mailing list <grass-dev at lists.osgeo.org>
Subject: [GRASS-dev] Parsing output of r.category which includes labels

If I am not wrong, all use cases of `read_command()` [0, 1], in (at least) the grass-addons repository, do not consider an output from `r.category` which includes labels.

[0] https://grass.osgeo.org/grass74/manuals/libpython/script.html?highlight=read_command#script.core.read_command
[1] https://grass.osgeo.org/grass75/manuals/libpython/script.html?highlight=read_command#script.core.read_command

I work on such a case where category numbers come along with label strings.
To read category numbers, I came up with:

import grass.script as grass
grass.read_command('r.category', map=base).split('\n')[:-1]

for category in categories:
        category = category.split('\t')[0] ```

Is there any other command that will do this better? Would you consider adding one?


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