[GIS] Calling GRASS functions from external Python

grasspython-2.7

I have GRASS 6.4.3 svn installed on my machine running Windows 7. Also in my machine, I installed Python 2.7.3 for Windows. Now I need to call GRASS libraries from Python and not within the Python shell in GRASS GUI itself. I set the environment variables in the env.bat for this. But connection fails. This is the env.bat I have:

set GISBASE=C:\Program Files\GRASS GIS 6.4.3svn

set HOME=%USERPROFILE%

set LD_LIBRARY_PATH = %GISBASE%\lib

set PATH= %GISBASE%\etc;%PATH%
set PATH=%GISBASE%\Python27;%PATH%
set PATH=%GISBASE%\lib;%GISBASE%\bin;%GISBASE%\extralib;%GISBASE%\msys\bin;%PATH%
set PATH=C:\Python27;%PATH%

set PYTHONLIB= C:\Python27;%PYTHONLIB%
set PYTHONPATH= %GISBASE%\etc\python;%PYTHONPATH%

rem Environmental variables for GRASS stand-alone installer

set GRASS_WISH=%GISBASE%\extrabin\wish.exe
set GRASS_PYTHON=python

set GRASS_PROJSHARE=%GISBASE%\proj
set GRASS_HTML_BROWSER=explorer
set GRASS_SH=%GISBASE%\msys\bin\sh.exe

set PYTHONHOME=%GISBASE%\Python27
set GDAL_DATA=%GISBASE%\share\gdal
set PROJ_LIB=%GISBASE%\proj
set GEOTIFF_CSV=%GISBASE%\share\epsg_csv

set PATH=%GISBASE%\msys\bin;%PATH%
set PATH=%GISBASE%\extrabin;%GISBASE%\extralib;%PATH%
set PATH=%GISBASE%\tcl-tk\bin;%GISBASE%\sqlite\bin;%GISBASE%\gpsbabel;%PATH%
set PATH=%GISBASE%\bin;%PATH%

rem Path to the python directory --
rem set PYTHONHOME=%GISBASE%\Python27 
rem if "x%GRASS_PYTHON%" == "x" set GRASS_PYTHON=python

Can somebody help me in rectifying the problem?

Best Answer

Check this page; it may give you some idea how to set it up:

http://grasswiki.osgeo.org/wiki/GRASS_and_Python

-> Creating Python scripts that call GRASS functionality from outside

--> MS-Windows

Related Solutions

[GIS] Running GRASS functions in QGIS 2.4 from python console

r.in.gdal is a command to import rasters into GRASS GIS, not into QGIS

There are two options to use GRASS GIS in QGIS:

1) with the grass plugin

you are working in GRASS GIS and you can use r.in.gdal in the Python console of GRASS GIS to import a raster into a Location/Mapset.

2) from processing

you are working in QGIS with a "virtual" Location/Mapset that has nothing to do with the Location/Mapset of 1), therefore r.in.gdal is useless -> use the the PyQGIS solution in the Python console of QGIS

You can also use osgeo.gdal to import a raster into a GRASS GIS Location/Mapset.

GRASS GIS – Connecting Python Script External to GRASS GIS 7 Program in Windows 10

The linked says you need to set environmental variables. This is done in Python using e.g.:

import os
os.environ['GISBASE'] = "/some/path"

The syntax

PYTHONPATH = 'C:\OSGeo4W\apps\grass\grass-7.0.4\etc\python'

in Python just sets a variable (global one in your case) which is just a Python variable, nothing more, nothing less. The aforementioned wiki just lists the environmental variables to be set. How you set them is up to you. You can do it ahead in the command line before starting Python, you can change it in the system (search the Internet for how to do it in some GUI for your version of MS Windows), or you can use Python (os.environ).

Here is an example how to setup the environment (simplified from GRASS Python doc):

import os
import sys
import subprocess

grass7bin = r'C:\Program Files\GRASS GIS 7.0.4\grass70.bat'
startcmd = [grass7bin, '--config', 'path']
try:
    p = subprocess.Popen(startcmd, shell=False,
                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = p.communicate()
except OSError as error:
    sys.exit("ERROR: Cannot find GRASS GIS start script"
             " {cmd}: {error}".format(cmd=startcmd[0], error=error))
if p.returncode != 0:
    sys.exit("ERROR: Issues running GRASS GIS start script"
             " {cmd}: {error}"
             .format(cmd=' '.join(startcmd), error=err))
gisbase = out.strip(os.linesep)

os.environ['GISBASE'] = gisbase
grass_pydir = os.path.join(gisbase, "etc", "python")
sys.path.append(grass_pydir)

import grass.script.setup as gsetup

gisdb = os.path.join(os.path.expanduser("~"), "Documents/grassdata")
location = "nc_spm_08"
mapset = "user1"

rcfile = gsetup.init(gisbase, gisdb, location, mapset)

# use grass functions here

os.remove(rcfile)

Now you put your GRASS module calls and GRASS Python API function calls to the place where # use grass functions here is.

Note that you don't do anything from the above if you just run the code from inside GRASS GIS session. However, the code once you have the environment done in the right way is the same and looks for example like this:

import grass.script as gscript

gscript.run_command('g.region', s=10, n=50, w=30, e=60, res=2)
gscript.mapcalc('test1 = sin(col() + row())')
print gscript.read_command('r.info', map='test1', flags='g')
print gscript.parse_command('r.univar', map='test1', flags='g')

Best Answer

Related Solutions

[GIS] Running GRASS functions in QGIS 2.4 from python console

GRASS GIS – Connecting Python Script External to GRASS GIS 7 Program in Windows 10

Related Question