I am trying to create a single side distance buffer around a line on QGIS.

Here is the code I am writing but I don't get the expected result:


Any idea?

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1 Answer 1


You're using a fixed distance buffer when you should be using a single sided buffer. Please see usage examples below.

For QGIS 3:

x = processing.run("qgis:singlesidedbuffer", {'INPUT':'input.shp','DISTANCE':10,'SIDE':0,'SEGMENTS':8,'JOIN_STYLE':0,'MITER_LIMIT':2,'OUTPUT':'memory:'})

For QGIS 2.X, 5th parameter indicates side (0=right, 1=left):

x = processing.runalg("gdalogr:singlesidedbuffersandoffsetlinesforlines","input.shp",0,"geometry","10",1,False,None,False,"",None)

To add the resulting layer to the map, use the following command:

layer = iface.addVectorLayer(x['OUTPUT_LAYER'], "Single Buffer", "ogr")
  • Sure, see edited answer.
    – 15Step
    Dec 25, 2018 at 17:12
  • Thank again, I think I am doing it wrong. Here is what I get when I run the code. FYI, the new shapefile (with the buffer) is not created. "processing.runalg("gdalogr:singlesidedbuffersandoffsetlinesforlines","input.shp",0,'geometry',10,1,False,None,False,None,"output.shp") {'OUTPUT_LAYER': 'output.shp'}" Dec 25, 2018 at 17:46
  • I think you're mixing the two usage examples. Try to use only the second line I wrote, changing the parameters appropriately (you also need to first import processing in case you didn't already). The OUTPUT_LAYER part shouldn't be used in QGIS 2.
    – 15Step
    Dec 25, 2018 at 18:16
  • Hi, So the code I wrote in my previous message i.e. {'OUTPUT_LAYER': 'output.shp'}" is actually something I get from the python consol after running the code : "processing.runalg("gdalogr:singlesidedbuffersandoffsetlinesforlines","input.shp",0,'geometry',10,1,False,None,False,"output.shp",None) Hence I guess there is another problem. Dec 25, 2018 at 18:26
  • There is no problem. The layer, as you showed, is generated correctly. The return value is a Python dictonary. See edited below above how to access the layer. Hope that works
    – 15Step
    Dec 26, 2018 at 17:11

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