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.enabled = True
    label.fieldName = '''concat('BASE: ' + to_string("''' + champNom1 + '''"),'\nL = ' + to_string("''' + champNom2 + '''") + 'm')'''
    label.placement= QgsPalLayerSettings.Line
    label.bufferDraw= True
    label.bufferSize= 1

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"
        # appliquer les couleurs selon le niveau de tension avec la fonction appCouleur ci-dessous
        # 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

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




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

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 ? gis.stackexchange.com/questions/258753/…
    – gisnside
    Oct 23, 2017 at 15:29
  • Can you try : self.iface.mapCanvas().refreshAllLayers()
    – sigeal
    Oct 31, 2017 at 18:52
  • Unfortunatly, it did not work too
    – ennine
    Oct 31, 2017 at 20:53
  • can you add which version of qgis you are using?
    – LaughU
    Nov 16, 2017 at 8:25
  • I am using the latest version QGis2.18.14
    – ennine
    Nov 17, 2017 at 13:58

2 Answers 2


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

label.placement = QgsPalLayerSettings.Line

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

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