Grass python shell can't find my data

Question

I have a problem, the grass 7 python shell can't find my rasters. When I try to use the python shell to set the region I get "region not found". I can set the region in the grass shell (and other tools I use can read the images from the grass shell), but I'm trying to develop a looping python code for a big part of my master's thesis and stop on this problem. I have the same problem on two computers, I'm using grass 7 (because of i.segment) on windows vista

The code I type into the python shell is: grass.run_command('g.region', region='xKM_430_420.1').

Am I typing the code in the wrong way? Should I use another command to set the region when using python? Or is it maybe some environmental variables?

Any ideas?

Answer 1

As you are working with GRASS 7, you can use (look at Workshop pygrass: modules):

1) grass.scriptwith the run_command(), read_command(),parse_command() functions or in pure Python

from grass.script import core as grass 
region = grass.parse_command('g.region', flags='p')
{'ellipsoid: international': None, 'zone: 0': None, 'north:131321.2037345': None, 'east:164555.24362815': None, 'cols: 30426': None, 'cells:354615030': None, 'nsres: 2.11689968': None, 'south: 106648.73800047': None, 'projection: 99 (Lambert Conformal Conic)': None, 'west:100152.80214237': None, 'datum: bel72': None, 'ewres: 2.11669104': None, 'rows:11655': None}
# or
region = grass.region()
region
{'rows': 11655, 'e': 164555.24362815, 'cells': 354615030, 'cols': 30426, 'n': 131321.20373450001, 's': 106648.73800047, 'w': 100152.80214237, 'ewres': 2.1166910400000001, 'nsres': 2.11689968}

For setting a region, look at Set Grass Region in Python grass.script

List of rasters

g.parse_command("g.list", _type="rast")
# or
grass.list_strings('rast')

2) pygrassin pure Python (look at pygrass or Workshop pygrass: GIS objects)

from grass.pygrass.modules.shortcuts import general as g
# an then call directly the module
g.region(flags='p') # and you can adapt the solution given above 
# or
from grass.pygrass.gis.region import Region
reg = Region()
reg.items()
[('proj', 99), ('zone', 0), ('north', 131321.20373450001), ('south', 106648.73800047), ('west', 100152.80214237), ('east', 164555.24362815), ('top', 1.0), ('bottom', 0.0), ('nsres', 2.1168996768794526), ('ewres', 2.1166910368033918), ('tbres', 1.0), ('rows', 11655), ('cols', 30426), ('cells', 354615030)]

List of rasters

rasters = g.mlist(type='rast')
# or
from grass.pygrass.gis import Mapset
m = Mapset()
m.glist('rast')

• Adam H: Thank you! This was really useful, I finally managed to type something into the python shell that worked. Both ways of calling the list of rasters worked and now I can set computational region using grass.read_command('g.region', flags='p', rast='xKm_440_430.1').
• Adam H: grass.read_command('i.segment') works as well. I am extremely thankful for this
• markusN: BTW: there is new documentation available: grasswiki.osgeo.org/wiki/…