#!/usr/bin/env python

import vtk

def main():
    # PART 1 Make some Data.
    # Make a tree.
    root = vtk.vtkMultiBlockDataSet()
    
    branch = vtk.vtkMultiBlockDataSet()
    root.SetBlock(0, branch)
    
    # Make some leaves.
    leaf1 = vtk.vtkSphereSource()
    leaf1.SetCenter(0,0,0)
    leaf1.Update()
    branch.SetBlock(0, leaf1.GetOutput())
    
    leaf2 = vtk.vtkSphereSource()
    leaf2.SetCenter(1.75,2.5,0)
    leaf2.SetRadius(1.5)
    leaf2.Update()
    branch.SetBlock(1, leaf2.GetOutput())
    
    leaf3 = vtk.vtkSphereSource()
    leaf3.SetCenter(4,0,0)
    leaf3.SetRadius(2)
    leaf3.Update()
    root.SetBlock(1, leaf3.GetOutput())
    
    # PART 2 Do something with the data
    # a non composite aware filter, the pipeline will iterate
    edges = vtk.vtkExtractEdges()
    edges.SetInputData(root)
    
    # PART 3 Show the data
    # also demonstrate a composite aware filter
    # this filter aggregates all blocks into one polydata
    # this is handy for display, although fairly limited
    # see vtkCompositePolyDataMapper2 for something better
    polydata = vtk.vtkCompositeDataGeometryFilter()
    polydata.SetInputConnection(edges.GetOutputPort())
  
    
    # Create the Renderer, RenderWindow, and RenderWindowInteractor.
    renderer = vtk.vtkRenderer()
    renderWindow  = vtk.vtkRenderWindow()
    renderWindow.AddRenderer(renderer)
    renderWindowInteractor = vtk.vtkRenderWindowInteractor()
    renderWindowInteractor.SetRenderWindow(renderWindow)
    
    mapper = vtk.vtkPolyDataMapper()
    mapper.SetInputConnection(0, polydata.GetOutputPort(0))
    actor = vtk.vtkActor()
    actor.SetMapper(mapper)

	# Enable user interface interactor.
    renderer.AddActor(actor)
    renderWindowInteractor.Start()
	
if __name__ == '__main__':
    main()

Create MultiBlockDataSet.py