Make many lines in one layer (Python)

Question

I what to create many lines with this code:

v_layer = QgsVectorLayer("LineString", "cable", "memory")
pr = v_layer.dataProvider()
seg = QgsFeature()
seg.setGeometry(QgsGeometry.fromPolyline([line_start, geomPoint]))
pr.addFeatures( [ seg ] )
v_layer.updateExtents()
QgsMapLayerRegistry.instance().addMapLayers([v_layer])

Buth this create one layer for each of this code.

How can I create all in one layer.

Answer 1

you need to add all the geometries before the addMapLayers

v_layer = QgsVectorLayer("LineString", "cable", "memory")
pr = v_layer.dataProvider()
# first element
seg = QgsFeature()
seg.setGeometry(QgsGeometry.fromPolyline([line_start, geomPoint]))
pr.addFeatures( [ seg ] )
v_layer.updateExtents()
# second element
seg = QgsFeature()
seg.setGeometry(QgsGeometry.fromPolyline([geomPoint, newgeomPoint]))
pr.addFeatures( [ seg ] )
v_layer.updateExtents()
# etc
......
QgsMapLayerRegistry.instance().addMapLayers([v_layer])

so use a for loop