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We can get point layer coordinates through the following code, but I want to know the coordinates of Line or MultiLine. How to get these coordinates?

layer = QgsProject.instance().mapLayersByName("layerName")[0]

features = layer.getFeatures()

for feature in features:
  geom = feature.geometry()
  print(geom.asPoint().x(), geom.asPoint().y())
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2 Answers 2

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For single part LineString:

layer = QgsProject.instance().mapLayersByName("Single parts")[0]

for feature in layer.getFeatures():
    for pnt in feature.geometry().asPolyline():
        print(pnt.x(), pnt.y())

For multipart LineString:

layer = QgsProject.instance().mapLayersByName("folyo")[0]

for feature in layer.getFeatures():
    for part in feature.geometry().asMultiPolyline():
        print("part")
        for pnt in part:
            print(pnt.x(), pnt.y())

Tested in QGIS 3.16.1

asMultiPolyline() and asPolyline() return a list of points, so you can use indexes.

To check the layer geometry type use the geometryType() method of a layer.

To separate single and multi types use the isSingleType() method.

Here is the code for it:

layer = QgsProject.instance().mapLayersByName("your_layer")[0]

if layer.geometryType() ==  QgsWkbTypes.LineGeometry:

    for feature in layer.getFeatures():
        geom = feature.geometry()

        if QgsWkbTypes.isSingleType(geom.wkbType()):
            # single
            for pnt in geom.asPolyline():
                print(pnt.x(), pnt.y())
        else:
            # multipart
            for part in geom.asMultiPolyline():
                print("part")
                for pnt in part:
                    print(pnt.x(), pnt.y())
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  • yeah it's correct, but if i don't know the layer type then how can I mention geom.asMultiPolyline(), it can be geom.asPolyline() or geom.asPoint(). "verts = geom.asMultiPolyline() # use geom.asPolyline() for line geometry" instead of hard coding to geom.asMultiPolyline(), can I use some run time API(). which will decide whether to use geom.asMultiPolyline()/ geom.asPolyline() or geom.asPoint()
    – xor
    Dec 3, 2020 at 9:06
  • See my updates in the answer
    – Zoltan
    Dec 3, 2020 at 11:13
3

If you want to extract the xy of vertices of a MultiPolyline geometry you can use the following code:

layer = QgsProject.instance().mapLayersByName("layerName")[0]

features = layer.getFeatures()
for feature in features:
    geom = feature.geometry()
    verts = geom.asMultiPolyline() # use geom.asPolyline() for line geometry
    for vert in verts:
        for i in range(len(vert)):
            print(vert[i].x(), vert[i].y())

The output will be like this:

-3487202.783144876 10010395.30478035
-3428476.505393841 10049595.900699263
-3428476.505393841 10049595.900699263
-3374593.995628879 9923727.261801671
-3428476.505393841 10049595.900699263
-3359626.0983730364 10059037.052994486

enter image description here

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  • yeah it's correct, but if i don't know the layer type then how can I mention geom.asMultiPolyline(), it can be geom.asPolyline() or geom.asPoint(). "verts = geom.asMultiPolyline() # use geom.asPolyline() for line geometry"
    – xor
    Dec 3, 2020 at 9:00
  • Add print(geom) to your code right after the geom variable, it will print the type of the geometry plus the coordinate of the vertices.
    – ahmadhanb
    Dec 3, 2020 at 9:15
  • But I want the coordinates separately.
    – xor
    Dec 3, 2020 at 10:45

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