I'm trying to code a script who calculate id of vineyard lines and vines in these lines.

I code with temporary layers, just my final layer will be save. But I'm getting stuck on adding new fields, at line 39, I have an OUTPUT error, and QGIS log says no more. Can you help me ?

This is my code :

##Intervine_distance=number 1.5
##output_layer=output vector

import os, processing
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from qgis.core import *
from qgis.gui import *

# Project Layer in L93

l93 = processing.runalg("qgis:reprojectlayer", point_layer, "EPSG:2154", None)

# Buffer


buffer = processing.runalg("qgis:fixeddistancebuffer", l93['OUTPUT'], 
Dbuf, 100, False, None )

# Dissolve

dissolve = processing.runalg("qgis:dissolve", buffer['OUTPUT'], True, '',  None) 

# Split

split = processing.runalg('qgis:multiparttosingleparts', dissolve['OUTPUT'], None)

#New Fields

rang = processing.runalg('qgis:addfieldtoattributestable', split['OUTPUT'], "Rang", 0, 3, 0, None)

pied = processing.runalg('qgis:addfieldtoattributestable', rang['OUTPUT'], "Pied", 0, 3, 0, None)

# Some steps remaind to code here

# Reproject Layer in WGS84

processing.runalg("qgis:reprojectlayer", pied, "EPSG:4326", output_layer)
  • What error are you getting? Jun 12, 2017 at 14:32
  • Welcome to GIS SE! As a new user please take the tour to learn about our focused Q&A format.
    – Midavalo
    Jun 12, 2017 at 15:18

1 Answer 1


I think you need to replace rang['OUTPUT'] with rang['OUTPUT_LAYER'] instead as the parameters for the qgis:addfieldtoattributestable algorithm reads:

ALGORITHM: Add field to attributes table
    INPUT_LAYER <ParameterVector>
    FIELD_NAME <ParameterString>
    FIELD_TYPE <ParameterSelection>
    FIELD_LENGTH <ParameterNumber>
    FIELD_PRECISION <ParameterNumber>
    OUTPUT_LAYER <OutputVector>

So instead use:

pied = processing.runalg('qgis:addfieldtoattributestable', rang['OUTPUT_LAYER'], "Pied", 0, 3, 0, None)

Then when you reproject, use :

processing.runalg("qgis:reprojectlayer", pied['OUTPUT_LAYER'], "EPSG:4326", output_layer)
  • 1
    Oh yes, that's it !! thank you for your help, and now I know where i have to search to solve these type of problems. I will be able to finish my script, or at least continue.
    – Tim C.
    Jun 12, 2017 at 14:59
  • 2
    @TimothéeColas The best way to say "thank you" here is to upvote and accept the answer. See What should I do when someone answers my question?
    – Midavalo
    Jun 12, 2017 at 15:18
  • 1
    Ok thank you for your advice, i'm a newbie on stackexchange ;)
    – Tim C.
    Jun 15, 2017 at 9:54
  • @TimothéeColas - Most welcome, glad it helped! And don't worry, you will get quickly used to stackexchange :)
    – Joseph
    Jun 15, 2017 at 9:59

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