Deleting vertices from line feature using PyQGIS

Question

I have a line made of 17959 nodes. I want to delete several range of nodes from that line with a Python command.

For example I want to delete all nodes between node 5530 to node 5861 and connect node 5530 to node 5861. Then I want to delete all nodes between node 14094 to node 14398 and connect node 14094 to node 14398.

Here is the raw code I am using now

layer = iface.addVectorLayer("input.shp", "", "ogr")
layer.startEditing()    
QgsVectorLayerEditUtils::deleteVertex(QgsFeatureId "input.shp", int vertex)

I am using QGIS 2.18.15

Answer 1

While it isn't deleting, per se, this will create a new feature with your desired geometry. I am not a fan of modifying original geometry as it can lead to data loss.

layer = iface.activeLayer()

features = layer.getFeatures()

for feat in features:
    line = feat.geometry().asMultiPolyline()

# debug
print (line)

# example uses only one feature
line = line[0]

section_1 = line[0:2]       # here you can specify your breaks
section_2 = [line[4]]       # if you have a single point, be sure to enclose it in [] so the list concatenation later works
section_3 = line[6:]        # my sample line only had 7 vertices

# concatenate your sections into a new list
new_coords = section_1 + section_2 + section_3

# make QgsPoints from the QgsPointXYs
new_coords = [QgsPoint(x) for x in new_coords]

# create a feature from your new coords list
new_line = QgsFeature()
new_line.setGeometry(QgsGeometry.fromPolyline(new_coords))

# if you want to add it to your existing layer
layer.dataProvider().addFeatures([new_line])

# if you want to add it to a new layer
new_layer = iface.addVectorLayer("LineString?crs=epsg:4326&field=id:integer&index=yes", "new layer", "memory")
new_layer.dataProvider().addFeatures([new_line])