I created some geoalgorithms with QGis and I need to use them in a Python script. By saving the layer obtained in a file having a specific path, I do not have problems. For example:

processing.runalg("modeler:esplodilinee", "buildings", "C:\prova\sides.shp") 
lines = iface.addVectorLayer("C:\prova\sides.shp", "poligon sides", "ogr") 

But I would not use a file, but rather a temporary variable, in order to re-use it within the specific script. The description of the algorithm suggests to me that:


So, I thought to do something like this:

OUTPUT_ALGQGISEXPLODELINES_1 = processing.runalg ("modeler: esplodilinee"
"buildings", None)
lines = processing.getObject (OUTPUT_ALGQGISEXPLODELINES_1)

But I get a mistake and not the desired results. Someone can help me?


It's correct to set the last parameter as None, so you create a .shp inside a temporary folder.

To get it: as you can see here the output of processing.runalg is a python dictionary.

So in your last code example you have to write OUTPUT_ALGQGISEXPLODELINES_1['OUTPUT'] instead of OUTPUT_ALGQGISEXPLODELINES_1 to get the path at the temporary layer.

The documentation is here and quite well written.

  • Thank you a lot. Unfortunately I didn't solve the problem. If I correct my code as follow: OUTPUT_ALGQGISEXPLODELINES_1= processing.runalg ("modeler: esplodilinee", "buildings", None) lines = processing.getObjectFromUri(OUTPUT_ALGQGISEXPLODELINES_1['OUTPUT']) I get an error: "TypeError: 'NoneType' object has no attribute 'getitem' ". Do you suggest me why? Thanks again. – Sara Gaudio Apr 24 '18 at 9:57
  • The processing.runalg() doesn't work and return a None object... 1) buildings is a QgsVectorLayer object? 2) Your model is working well outside the script? The input parameter is only one? – Oscar Campo Apr 24 '18 at 10:03
  • 1)yes, it is a polygon layer. 2) the model works well outside the script and also when I fix a specific filepath (as in my first example) – Sara Gaudio Apr 24 '18 at 10:05
  • I edited my previous comment – Oscar Campo Apr 24 '18 at 10:06
  • 1
    Me too :) I would notice you that the error is linked to code line "lines = processing.getObjectFromUri(OUTPUT_ALGQGISEXPLODELINES_1['OUTPUT'])" and not to the model. – Sara Gaudio Apr 24 '18 at 10:10

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