VTK/Examples/Python/Graphs/SelectedVerticesAndEdges

import vtk
 
source = vtk.vtkRandomGraphSource()
source.Update()
 
view = vtk.vtkGraphLayoutView()
view.AddRepresentationFromInputConnection(source.GetOutputPort())
 
def selectionCallback(caller, event):
       # In C++ there is some extra data passed to the callback, but in Python
       # the callback data is lost...
 
       # There should be two selection nodes, but which one is vertices and which is edges
       # does not seem to be guaranteed...
       sel = caller.GetCurrentSelection()
       node0 = sel.GetNode(0)
       node0_field_type = node0.GetFieldType()
       sel_list0 = caller.GetCurrentSelection().GetNode(0).GetSelectionList()
       node1 = sel.GetNode(1)
       node1_field_type = node1.GetFieldType()
       sel_list1 = caller.GetCurrentSelection().GetNode(1).GetSelectionList()
 
       if (sel_list0.GetNumberOfTuples() > 0):
               printFieldType(node0_field_type)
               for ii in range(sel_list0.GetNumberOfTuples()):
                       print "\t", sel_list0.GetValue(ii)
 
       if (sel_list1.GetNumberOfTuples() > 0):
               printFieldType(node1_field_type)
               for ii in range(sel_list1.GetNumberOfTuples()):
                       print "\t", sel_list1.GetValue(ii)
 
       print "- - -"
 
def printFieldType(field_type):
       if field_type == 3:
               print "Vertices Selected:"
       elif field_type == 4:
               print "Edges Selected:"
       else:
               print "Unknown type:"
 
rep = view.GetRepresentation(0)
 
# The vtkRenderedGraphRepresentation should already have a vtkAnnotationLink,
# so we just want to grab it and add an observer with our callback function attached
link = rep.GetAnnotationLink()
link.AddObserver("AnnotationChangedEvent", selectionCallback)
 
view.GetRenderWindow().SetSize(600, 600)
view.ResetCamera()
view.Render()
view.GetInteractor().Start()