actionspyqgisqgis
I have a table with three attributes [field1, field2, field3].
I'm trying to insert a new feature to this table by defining field2 and field3 only.
lyr = QgsMapLayerRegistry.instance().mapLayer('layer')
new_feat = QgsFeature()
new_feat.setAttribute(1,"text1")
new_feat.setAttribute(2,"text2")
lyr.dataProvider().addFeatures([new_feat])
lyr.commitChanges()
It seems that I have a problem with the index in the setAttribute.
What am I missing?
So, for the first python script for QGIS, I have:
from qgis.core import *
from PyQt4.QtCore import *
from PyQt4 import QtGui, QtCore
import math
COMP = 1.0
FACS = 0.0
ORIG = 1.0
OROM = 1.0
ORZE = 1.0
coeff_a = 1.6
coeff_b = 3
seuil_1 = 1000000
seuil_2 = 300000000
# supply path to where is your qgis installed
QgsApplication.setPrefixPath("/path/to/qgis/installation", True)
# load providers
QgsApplication.initQgis()
# To load the shapefile - for the first time only
#layer = QgsVectorLayer("./shape/Portefeuille/portefeuille_jointure.shp", "portefeuille", "ogr")
#QgsMapLayerRegistry.instance().addMapLayer(layer)
#
# To add columns : - for the first time only
#caps = layer.dataProvider().capabilities()
#if caps & QgsVectorDataProvider.AddAttributes:
# res = layer.dataProvider().addAttributes([QgsField("Delivrance", QVariant.Double)])
#if caps & QgsVectorDataProvider.AddAttributes:
# res = layer.dataProvider().addAttributes([QgsField("Age_corr", QVariant.Double)])
#if caps & QgsVectorDataProvider.AddAttributes:
# res = layer.dataProvider().addAttributes([QgsField("Parametre", QVariant.Double)])
#if caps & QgsVectorDataProvider.AddAttributes:
# res = layer.dataProvider().addAttributes([QgsField("Classe", QVariant.Int)])
#
# To retain the right layer by its name:
layers = iface.legendInterface().layers()
for layer in layers:
name = layer.name()
if name.endswith('portefeuille'):
provider = layer.dataProvider()
updateMap = {}
# To find the right id of the fields I need:
idORIGINE=provider.fields().indexFromName( 'ORIGINE' )
idAGE=provider.fields().indexFromName( 'AGE' )
idDEL_Z=provider.fields().indexFromName( 'DEL_Z' )
idCESS_Z=provider.fields().indexFromName( 'CESS_Z' )
idDEL_G=provider.fields().indexFromName( 'DEL_G' )
idCESS_G=provider.fields().indexFromName( 'CESS_G' )
idDEL_CL=provider.fields().indexFromName( 'DEL_CL' )
idCESS_CL=provider.fields().indexFromName( 'CESS_CL' )
idDelivrance=provider.fields().indexFromName( 'Delivrance' )
idAge_corr=provider.fields().indexFromName( 'Age_corr' )
idParametre=provider.fields().indexFromName( 'Parametre' )
idClasse=provider.fields().indexFromName( 'Classe' )
iter = provider.getFeatures()
# Loop on every feature to update somme attributes:
for feature in iter:
# Processing of Delivrance by addition:
Delivrance = feature.attributes()[idDEL_Z] + feature.attributes()[idCESS_Z] + feature.attributes()[idDEL_G] + feature.attributes()[idCESS_G] + feature.attributes()[idDEL_CL] + feature.attributes()[idCESS_CL]
# Processing of 'Age_corr':
coeff=0
if feature.attributes()[idORIGINE] == "COMP":
coeff=COMP
if feature.attributes()[idORIGINE] == "FACS":
coeff=FACS
if feature.attributes()[idORIGINE] == "ORIG":
coeff=ORIG
if feature.attributes()[idORIGINE] == "OROM":
coeff=OROM
if feature.attributes()[idORIGINE] == "ORZE":
coeff=ORZE
Age_corr = (1+coeff)*feature.attributes()[idAGE]
# Processing of 'Parametre':
Parametre = math.pow(Age_corr,coeff_b) * math.pow(Delivrance,coeff_a)
# Processing of Classe:
Classe=2 # Default
if Parametre < seuil_1:
Classe=1
if Parametre > seuil_2:
Classe=3
# To print the result, just for debug:
# print Classe
# To update the fields processed:
updateMap[feature.id()] = {idDelivrance: Delivrance , idAge_corr: Age_corr , idParametre: Parametre , idClasse: Classe }
# To save the result
provider.changeAttributeValues( updateMap )
# I would like to update the map... Here it is:
iface.mapCanvas().refresh()
# I would like to refresh the number of features in the layer on the map...
# so I'm loofing for...
# Just to verify that the process ends
print "Done"
It's what I want for this first use of QGIS python script.
First possibility: use concat and replace double commas where you have empty entries:
replace( concat (field_a,', ',field_b,', ',field_c), ', ,', ',')
Second possibility: use arrays to concatenate, they concatenate NULL values as empty strings that you can then remove. Use one of this expressions:
replace( array_to_string (array (field_a,field_b,field_c)),',,',',')
Or, alternatively:
array_to_string (array_remove_all (array (field_a,field_b,field_c),''))
Best Answer
You must declare the feature's fields before being able to use them: