Selecting lines of shortest path between two points (QGIS)

Question

I am looking for a method to automatically select the lines of a shortest path between two points. Theoretically it is the Road Graph plugin, which is now the "shortest path point to point" function in QGIS. My problem is that I don't want to create a new shapefile. I want to select the lines in the shapefile I am working with to insert data into the attribute table.

How can I solve this problem? I tried using Python, but I am new to Python and the scripts I tried don't work. For example, I found this script(https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/network_analysis.html?highlight=shortest#finding-shortest-paths). But nothing happens when I run it.

from qgis.core import *
from qgis.gui import *
from qgis.analysis import *

from qgis.PyQt.QtCore import *
from qgis.PyQt.QtGui import *

vectorLayer = QgsVectorLayer('testdata/network.gpkg|layername=network_lines', 'lines')
builder = QgsGraphBuilder(vectorLayer.sourceCrs())
director = QgsVectorLayerDirector(vectorLayer, -1, '', '', '', QgsVectorLayerDirector.DirectionBoth)

startPoint = QgsPointXY(1179661.925139,5419188.074362)
endPoint = QgsPointXY(1180942.970617,5420040.097560)

tiedPoints = director.makeGraph(builder, [startPoint, endPoint])
tStart, tStop = tiedPoints

graph = builder.graph()
idxStart = graph.findVertex(tStart)

tree = QgsGraphAnalyzer.shortestTree(graph, idxStart, 0)

idxStart = tree.findVertex(tStart)
idxEnd = tree.findVertex(tStop)

if idxEnd == -1:
    raise Exception('No route!')

# Add last point
route = [tree.vertex(idxEnd).point()]

# Iterate the graph
while idxEnd != idxStart:
    edgeIds = tree.vertex(idxEnd).incomingEdges()
    if len(edgeIds) == 0:
        break
    edge = tree.edge(edgeIds[0])
    route.insert(0, tree.vertex(edge.fromVertex()).point())
    idxEnd = edge.fromVertex()

# Display
rb = QgsRubberBand(iface.mapCanvas())
rb.setColor(Qt.green)

# This may require coordinate transformation if project's CRS
# is different than layer's CRS
for p in route:
    rb.addPoint(p)

Answer 1

from qgis.core import QgsProject, QgsVectorLayer, QgsPointXY
from qgis.analysis import QgsNetworkAnalyzer


network_layer_path = '/path/to/network_layer.shp'
start_point = QgsPointXY(10, 10)
end_point = QgsPointXY(20, 20)


network_layer = QgsVectorLayer(network_layer_path, 'Network Layer', 'ogr')
network_analyzer = QgsNetworkAnalyzer()
director = network_analyzer.buildNetwork(network_layer, [], [], [], QgsNetworkAnalyzer.DirectionFlagBoth, 5)

# Find the closest graph points to the start and end points
start_id = director.nearestNodeOnNetwork(start_point, QgsNetworkAnalyzer.DirectionFlagBoth)
end_id = director.nearestNodeOnNetwork(end_point, QgsNetworkAnalyzer.DirectionFlagBoth)
(success, path) = network_analyzer.shortestPath(start_id, end_id)
line_ids = path.links()
network_layer.selectByIds(line_ids)
network_layer.triggerRepaint()

# Save the selected lines to a new layer if needed
selected_layer_path = '/path/to/selected_lines.shp'
QgsVectorLayer.exportNamedLayerDefinition(network_layer, selected_layer_path)