qgis_network_analysis

qgis_network_analysis.py

project = QgsProject.instance()

start_points = project.mapLayersByName('start_points')[0] # start
end_points = project.mapLayersByName('end_points')[0] # end
network = project.mapLayersByName('network')[0] # network


## from polyline to director
director = QgsVectorLayerDirector(
    source=network,
    directionFieldId=-1, 
    directDirectionValue='',
    reverseDirectionValue='',
    bothDirectionValue='',
    defaultDirection=0 # only forward
)

# adding the strategy
strategy = QgsNetworkDistanceStrategy()
director.addStrategy(strategy)

# initialzie the graph builder (no snap at all)
builder = QgsGraphBuilder(
    network.crs(),
    True,
    0
)

# loop on the start point features
for i in start_points.getFeatures():
    
    igeom = i.geometry()
    
    # get the geometry as QgsPointXY
    start_point = igeom.asPoint()
    
    # loop on the end point faetures
    for k in end_points.getFeatures():
        
        # get the geometry as QgsPointXY
        kgeom = k.geometry()
        end_point = kgeom.asPoint()
        
        # here QGIS explodes !
        tiedPoints = director.makeGraph(builder, [start_point, end_point])
        graph = builder.graph()
        
        idxStart = graph.findVertex(tiedPoints[0])
        idxEnd = graph.findVertex(tiedPoints[1])
        
        (tree, costs) = QgsGraphAnalyzer.dijkstra(graph, idxStart, 0)
        
        if idxEnd != -1:
            cost = costs[idxEnd]
            
            print(cost)