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Using Qgis 2.14.12 and PyQGIS, I get an error message when executing the following:

processing.runalg('grass7:v.surf.idw', layer, 18, 2.0, 'p', True, "%f, %f, %f ,%f"%(1.635, 1.813, 50.896,  51.0205), 0.005, -1, 0.001, "e://out.tif")

The output from 

layer.isValid()

is True, but I get this error (warning) in the Python Console :

C:\PROGRA~1\QGIS2~1.14\bin>g.region n= 51.020500 s= 50.896000 e= 1.813000 w=1.635000 res=0.005                  
   Sorry, <51.020500> isn't a valid option                  
   Sorry, <50.896000> isn't a valid option                  
   Sorry, <1.813000> isn't a valid option

This results in a 1 km raster at lat/lon 0/0.

However, when I launch the function from the QGIS toolbox, the output is fine.

I've tried both with GRASS 6 & 7.

Any ideas?

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1 Answer 1

Reset to default
3

The syntax seems to be correct, but you need to remove the blank space when specifying the extent. Try replacing:

"%f, %f, %f ,%f"%(1.635, 1.813, 50.896,  51.0205)

with:

"%f,%f,%f,%f" %(1.635, 1.813, 50.896,  51.0205)

In this way, you will write it as a string.

The working command should be:

processing.runalg('grass7:v.surf.idw', layer, 18, 2.0, 'p', True, "%f,%f,%f,%f"%(1.635, 1.813, 50.896,  51.0205), 0.005, -1, 0.001, "e://out.tif")
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14
  • I tried that prior to using %f, but still giving me that error. What i don't get is that it works fine though the toolbox.
    – julsbreakdown
    Commented Mar 28, 2017 at 13:15
  • @julsbreakdown Why did you specify 0.005 as output size of the cell? a 5 mm resolution raster seems is not so common. Furthermore, 0.001 should be 0.0001 if left as default value. What about using 0 instead of 0.005 and 0.0001 instead of 0.001?
    – mgri
    Commented Mar 28, 2017 at 13:22
  • for the default value 0.001 that was a typo, for the resolution i tried giving a aberrant value to see if it made a difference. But even with default values a still get the error/warning message
    – julsbreakdown
    Commented Mar 28, 2017 at 13:44
  • 1
    Run the algorithm from the Processing Toolbox and then go to Processing > History, open the ALGORITHM folder (it displays all the operations you ran from Processing). Try to find the differences with your script: is it equals to yours?
    – mgri
    Commented Mar 28, 2017 at 14:08
  • 1
    I think it should be useful to others if I edit my answer including the final solution instead of the first one I provided, so you may accept it for helping other future readers.
    – mgri
    Commented Mar 28, 2017 at 14:25

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