Multi-field labeling of shapefile with PyQGIS

Question

I wrote the following code in order to draw the line labels with multiple fields. However, the label do not appear automatically in QGIS and I have to switch the "Layer Properties/Labels", and toggle OK.

def labelLine(lyr, champNom1, champNom2):
    label = QgsPalLayerSettings()
    label.readFromLayer(lyr)
    label.enabled = True
    label.fieldName = '''concat('BASE: ' + to_string("''' + champNom1 + '''"),'\nL = ' + to_string("''' + champNom2 + '''") + 'm')'''
    label.placement= QgsPalLayerSettings.Line
    label.bufferDraw= True
    label.bufferSize= 1
    label.setDataDefinedProperty(QgsPalLayerSettings.Size,True,True,'8','')
    label.writeToLayer(lyr)
def saveCoucheFRAC():
    layer = iface.activeLayer()
    nom = nom2 + "_FRAC"
    lien = path2 + "_FRAC" + ".shp"
    QgsVectorFileWriter.writeAsVectorFormat(layer, lien, "utf-8", QgsCoordinateReferenceSystem(22332, QgsCoordinateReferenceSystem.EpsgCrsId), "ESRI Shapefile")
    #Charger cette couche dans QGis
    vlayer = QgsVectorLayer(lien, nom, "ogr")
    if not vlayer.isValid():
        print " Verifier la validite du fichier"
    else:
        # appliquer les couleurs selon le niveau de tension avec la fonction appCouleur ci-dessous
        appCouleur(vlayer)
        # changer l'epaisseur de la couche ligne
        epaiLyr(vlayer, "0.7")
        # ajouter l'etiquette de longueur sur chaque segment
        labelLine(vlayer, "BASE", "Longueur_m")
        # Definir la visibilite de la couche entre ech min 0 et max 100 000
        visLyr(vlayer, 0, 100000)
        #Charger dans le Canvas
        QgsMapLayerRegistry.instance().addMapLayer(vlayer)
saveCoucheFRAC()

I try to add the following to enable the label draw but it does not work:

layer.triggerRepaint()

or

layer.commitChanges()
layer.updateExtents()

A screenshot of the map (After toggling OK, line labels appears in QGIS)

Could you paste a screenshot or an example of what is should be doing ? Is this question a duplicate of this one ? https://gis.stackexchange.com/questions/258753/multi-line-labeling-of-a-shapefile-layer-with-pyqgis — gisnside, Oct 23 '17 at 15:29

score 1 · Answer 1 · answered May 17 '19 at 20:19

1

It seems you need to define the placement for line geometries.

label.placement = QgsPalLayerSettings.Line

answered May 17 '19 at 20:19

Matt

16,843
3
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score -1 · Answer 2 · edited Aug 27 '21 at 07:40

-1

You should add this statement： settings.isExpression = True. This can be used to display multiple labels!

edited Aug 27 '21 at 07:40

Kadir Şahbaz

76,800
56
247
389

answered Aug 27 '21 at 03:08

汪超强

1

Multi-field labeling of shapefile with PyQGIS

2 Answers2

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