I call using processing.alghelp("grass:r.to.vect")

I looked input:

feature <ParameterSelection>
-s <ParameterBoolean>
output <OutputVector>

feature(Feature type)
    0 - line
    1 - point
    2 - area
GRASS_OUTPUT_TYPE_PARAMETER(v.out.ogr output type)
    0 - auto
    1 - point
    2 - line
    3 - area

then I try to do , processing.runalg("grass:r.to.vect" , iface.activeLayer,2, True, None,3,r"C:\Users\user2\Desktop\1\temp\drfsg\zhopa.shp")") but it returns an error, what I did wrong? the project is only one raster layer

  • You should use correct path-notation in strings: r"C:\Users\user2\Desktop\1\temp\drfsg" or "C:/Users/user2/Desktop/1/temp/drfsg" or "C:\\Users\\user2\\Desktop\\1\\temp\\drfsg" Don't know if thats the issue.. Feb 9, 2017 at 9:42
  • that is not the way, it gives another error , 'int' object has no attribute 'split'
    – frontend33
    Feb 9, 2017 at 9:44
  • 1
    I think your GRASS_REGION_PARAMETER needs no int (your value is 2) but should be a string like it was used here: gis.stackexchange.com/questions/75666/… Feb 9, 2017 at 9:58
  • processing.runalg("grass:r.to.vect" , iface.activeLayer,2, True, None,3,r"C:\Users\user2\Desktop\1\temp\drfsg\zhopa.shp") writing does not issue error, but nothing happens, does not work
    – frontend33
    Feb 9, 2017 at 10:05
  • if the code runs without an error than it is likely a problem with the dataset used. Data values, data size, for example. So please give more information about what you trying to achieve. Feb 9, 2017 at 10:14

1 Answer 1


The recent QGIS versions have implemented GRASS7 into its processing framework as default so you may need to use grass7:r.to.vect instead of grass:r.to.vect. I have also experienced issues when trying to set the GRASS_REGION_PARAMETER to blank, instead I use the extents of the input layer as that's usually what I am interested in.

So you could try the following code into the python console:

from PyQt4.QtCore import QFileInfo
import processing

# Identify raster layer
raster = iface.activeLayer()
fileName = raster.source()
fileInfo = QFileInfo(fileName)
baseName = fileInfo.baseName()
rlayer = QgsRasterLayer(fileName, baseName)

# Define the extent of the region
extent = rlayer.extent()
xmin = extent.xMinimum()
xmax = extent.xMaximum()
ymin = extent.yMinimum()
ymax = extent.yMaximum()

processing.runalg("grass7:r.to.vect",rlayer,2,True,"%f,%f,%f,%f"% (xmin, xmax, ymin, ymax),3,"C:/Users/user2/Desktop/1/temp/drfsg/zhopa.shp")
  • thank you very much it works on both the version Qgis 12.8 and 12.2 as ))) Is it possible in this vector layer to make more transparent the fill?
    – frontend33
    Feb 9, 2017 at 10:38
  • @АзаматВалиев - Most welcome, glad it worked! You can make it transparent by changing its style properties by right-clicking the layer and going to Properties > Style :)
    – Joseph
    Feb 9, 2017 at 10:47
  • and whether it is an important question, Grass gis 7 coverage of the region, select the coverage on the map instead of coordinates?
    – frontend33
    Feb 9, 2017 at 10:48
  • and about transparency, I'm doing a module, so that would not have to manually change namely through the console
    – frontend33
    Feb 9, 2017 at 10:49
  • @АзаматВалиев - You can define your own coordinates by replacing "%f,%f,%f,%f"% (xmin, xmax, ymin, ymax) with "0.0, 1.0, 2.0, 3.0" (note they are inside a string). If you want to change the transparency of the layer, there are a number of posts asked here on GIS:SE such as this one: How do I set layer transparency in QGIS 2.0 with Python?
    – Joseph
    Feb 9, 2017 at 10:55

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