Getting temporary result in PyQGIS

Question

I wanted to use temporary results in my pyqgis script just like

import processing
from qgis.core import *

carte_init=processing.getObject("carte_postes")

extent = "%s,%s,%s,%s" % ( carte_init.extent().xMinimum(), 
carte_init.extent().xMaximum(), carte_init.extent().yMinimum(), 
carte_init.extent().yMaximum() )

# Exrtacting test posts centroids
postes= processing.runalg('qgis:saveselectedfeatures', carte_init, None)
centroides_postes=processing.runalg('qgis:polygoncentroids', 
postes['OUTPUT'], None)
voronoi_max_extent=processing.runalg('grass7:v.voronoi', 
centroides_postes['OUTPUT'], False, False, extent,  -1, 0, 0, None) }

But I get the following when I run it in the python console...

Traceback (most recent call last):
File "<input>", line 1, in <module>
KeyError: 'OUTPUT'

As it works perfectly well in this script

import processing
from qgis.core import *

layer=processing.getObject("carte")
layer.invertSelection()

tampon_plus = processing.runalg('qgis:fixeddistancebuffer', layer, 
"20","5",False, None)
dissolve = processing.runalg('qgis:dissolve', tampon_plus['OUTPUT'], True, 
None, None)
carte_finale = processing.runalg('qgis:fixeddistancebuffer', 
dissolve['OUTPUT'], "-20","5",False, 
"c:/Users/LENOVO/Desktop/zones/carte_finale.shp")}

I wonder where is my mistake. I tried to use algorithm ['Result'] just as in Saving layer as temporary file usig PyQGIS? but it's not working any better.

Answer 1

You need to use ['OUTPUT_LAYER'] instead of ['OUTPUT']. You can see this if you type in the Python Console:

>>>import processing
>>>processing.alghelp('qgis:saveselectedfeatures')
ALGORITHM: Save selected features
    INPUT_LAYER <ParameterVector>
    OUTPUT_LAYER <OutputVector>

Both qgis:saveselectedfeatures and qgis:polygoncentroids algorithms require this.

---

So try running the following:

import processing
from qgis.core import *

carte_init=processing.getObject("carte_postes")

extent = "%s,%s,%s,%s" % ( carte_init.extent().xMinimum(), 
carte_init.extent().xMaximum(), carte_init.extent().yMinimum(), 
carte_init.extent().yMaximum() )

# Exrtacting test posts centroids
postes= processing.runalg('qgis:saveselectedfeatures', carte_init, None)
centroides_postes=processing.runalg('qgis:polygoncentroids', 
postes['OUTPUT_LAYER'], None)
voronoi_max_extent=processing.runalg('grass7:v.voronoi', 
centroides_postes['OUTPUT_LAYER'], False, False, extent,  -1, 0, 0, None)