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Hi Pietro, Thanks for the explanation!<br>
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<div class="moz-cite-prefix">On 22-07-14 15:05, Pietro wrote:<br>
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cite="mid:CAM_TVRLsLcKQsPiw5d3pF2ug99_Z7xZTsdWrVyCnsokNor56iA@mail.gmail.com"
type="cite">
<pre wrap="">Hi Paulo,
On Tue, Jul 22, 2014 at 8:55 AM, Paulo van Breugel
<a class="moz-txt-link-rfc2396E" href="mailto:p.vanbreugel@gmail.com"><p.vanbreugel@gmail.com></a> wrote:
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<pre wrap="">I am trying to familiarize myself a bit with python scripting in GRASS. I am
a bit confused about the different approaches that seem possible. More
specifically, there is the pygrass
(<a class="moz-txt-link-freetext" href="http://grasswiki.osgeo.org/wiki/Python/pygrass">http://grasswiki.osgeo.org/wiki/Python/pygrass</a>) and grass python scripting
library (
<a class="moz-txt-link-freetext" href="http://grasswiki.osgeo.org/wiki/GRASS_Python_Scripting_Library">http://grasswiki.osgeo.org/wiki/GRASS_Python_Scripting_Library</a>). Is there
somewhere a concise description explaining the difference between the two.
</pre>
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<pre wrap="">
I tried to explain the different approach in the following article:
Zambelli, P., Gebbert, S., Ciolli, M., 2013. Pygrass: An Object
Oriented Python Application Programming Interface (API) for Geographic
Resources Analysis Support System (GRASS) Geographic Information
System (GIS). ISPRS International Journal of Geo-Information 2,
201–219.
<a class="moz-txt-link-freetext" href="http://dx.doi.org/10.3390/ijgi2010201">http://dx.doi.org/10.3390/ijgi2010201</a>
<a class="moz-txt-link-freetext" href="http://www.mdpi.com/2220-9964/2/1/201/pdf">http://www.mdpi.com/2220-9964/2/1/201/pdf</a>
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<pre wrap="">And for writing python scripts (addons), which of these two are a better
option to use (for somebody fairly familiar with GRASS, with some experience
in writing shell or R scripts for GRASS, but with no experience at all with
python).
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<pre wrap="">
pygrass has been written to be as much pythonic as possible, therefore
for people knowing python should be easier to work with pygrass.
In general I think that the grass.script API is more tested and stable
and more important it is working for both GRASS6 and GRASS7.
pygrass.Module has been devloped to interact with a module as an
object, setting the module parameters, check if the parameters are
valid or not, and execute the module. The Module class has been used
to apply a GRASS module over the current region, splitting the region
in several tiles, create a mapset for each tile, execute the module
and then patch the results and remove the temporary mapset
(GridModule), or in ParallelModuleQueue to handle a queue of modules.
If combine with shortcuts can Improve the python syntax:
from:
run_command("r.slope.aspect", elevation="elevation", slope="slope",
overwrite=True)
to:
r.slope_aspect(elevation="elevation", slope="slope", overwrite=True)
that is closer to the BASH syntax.
But what is particularly interesting of pygrass is the ability to use
and call the C API of GRASS through the ctypes , all the functions in
the grass.script modules are calling and parsing the results of some
GRASS modules.
With pygrass we are using directly the C API of GRASS, like for
example you can write a function that work row by row or pixel by
pixel to do some analysis on a raster map, or line by line in a vector
map, and user don't have to know C or the C API of GRASS.
I hope that the difference is clearer now, otherwise please ask me! :-)
Pietro
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