Documentation/Nightly/ScriptRepository

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Contents


Community-contributed modules

Usage: save the .py file to a directory, add the directory to the additional module paths in the Slicer application settings (choose in the menu: Edit / Application settings, click Modules, click >> next to Additional module paths, click Add, and choose the .py file's location).

Filters

DICOM

Informatics

  • MarkupsInfo.py: Compute the total length between all the points of a markup list.
  • LineProfile.py: Compute intensity profile in a volume along a line.

Community-contributed examples

Usage: Copy-paste the shown code lines or linked .py file contents into Python console in Slicer.

Capture

  • Get a MRML node in the scene based on the node name and call methods of that object. For the MRHead sample data:
 vol=slicer.util.getNode('MR*')
 vol.GetImageData().GetDimensions()
  • Capture the full Slicer screen and save it into a file
 img = qt.QPixmap.grabWidget(slicer.util.mainWindow()).toImage()
 img.save('c:/tmp/test.png')

Launching Slicer

  • How to open an .mrb file with Slicer at the command line?
 Slicer.exe --python-code "slicer.util.loadScene( 'f:/2013-08-23-Scene.mrb' )"
  • How to run a script in the Slicer environment in batch mode (without showing any graphical user interface)?
 Slicer.exe --python-code "doSomething; doSomethingElse; etc." --testing --no-splash --no-main-window

Load volume from file

When loading a volume from file, it is recommended to set returnNode=True to retrieve the loaded volume node. 

[success, loadedVolumeNode] = slicer.util.loadVolume('c:/Users/abc/Documents/MRHead.nrrd', returnNode=True)

DICOM

How to access tags of DICOM images imported into Slicer? For example, to print the first patient's first study's first series' "0020,0032" field:

 db=slicer.dicomDatabase
 patientList=db.patients()
 studyList=db.studiesForPatient(patientList[0])
 seriesList=db.seriesForStudy(studyList[0])
 fileList=db.filesForSeries(seriesList[0])
 print db.fileValue(fileList[0],'0020,0032')

How to access tag of a volume loaded from DICOM? For example, get the patient position stored in a volume:

 volumeName='2: ENT IMRT'
 n=slicer.util.getNode(volumeName)
 instUids=n.GetAttribute('DICOM.instanceUIDs').split()
 filename=slicer.dicomDatabase.fileForInstance(instUids[0])
 print slicer.dicomDatabase.fileValue(filename,'0018,5100')

How to access tag of an item in the Subject Hierachy tree? For example, get the content time tag of a structure set:

 rtStructName = '3: RTSTRUCT: PROS'
 rtStructNode = slicer.util.getNode(rtStructName)
 shNode = slicer.vtkMRMLSubjectHierarchyNode.GetSubjectHierarchyNode(slicer.mrmlScene)
 rtStructShItemID = shNode.GetItemByDataNode(rtStructNode)
 ctSliceInstanceUids = shNode.GetItemAttribute(rtStructShItemID, 'DICOM.ReferencedInstanceUIDs').split()
 filename = slicer.dicomDatabase.fileForInstance(ctSliceInstanceUids[0])
 print slicer.dicomDatabase.fileValue(filename,'0008,0033')

How can I convert DICOM to NRRD on the command line?

/Applications/Slicer-4.6.2.app/Contents/MacOS/Slicer --no-main-window --python-code "node=slicer.util.loadVolume('/tmp/series/im0.dcm', returnNode=True)[1]; slicer.util.saveNode(node, '/tmp/output.nrrd'); exit()"

The same can be done on windows by using the top level Slicer.exe. Be sure to use forward slashes in the pathnames within quotes on the command line.

Toolbar functions

  • How to turn on slice intersections in the crosshair menu on the toolbar:
 viewNodes = slicer.mrmlScene.GetNodesByClass('vtkMRMLSliceCompositeNode')
 viewNodes.UnRegister(slicer.mrmlScene)
 viewNodes.InitTraversal()
 viewNode = viewNodes.GetNextItemAsObject()
 while viewNode:
   viewNode.SetSliceIntersectionVisibility(1)
   viewNode = viewNodes.GetNextItemAsObject()

How to find similar functions? For this one I searched for "slice intersections" text in the whole slicer source code, found that the function is implemented in Base\QTGUI\qSlicerViewersToolBar.cxx, then translated the qSlicerViewersToolBarPrivate::setSliceIntersectionVisible(bool visible) method to Python.

Manipulating objects in the slice viewer

  • How to define/edit a circular region of interest in a slice viewer?

Drop two markup points on a slice view and copy-paste the code below into the Python console. After this, as you move the markups you’ll see a circle following the markups. 

# Update the sphere from the fiducial points
def UpdateSphere(param1, param2):  
  import math
  centerPointCoord = [0.0, 0.0, 0.0]
  markups.GetNthFiducialPosition(0,centerPointCoord)
  circumferencePointCoord = [0.0, 0.0, 0.0]
  markups.GetNthFiducialPosition(1,circumferencePointCoord)
  sphere.SetCenter(centerPointCoord)
  radius=math.sqrt((centerPointCoord[0]-circumferencePointCoord[0])**2+(centerPointCoord[1]-circumferencePointCoord[1])**2+(centerPointCoord[2]-circumferencePointCoord[2])**2)
  sphere.SetRadius(radius)
  sphere.SetPhiResolution(30)
  sphere.SetThetaResolution(30)
  sphere.Update()

# Get markup node from scene
markups=slicer.util.getNode('F')
sphere = vtk.vtkSphereSource()
UpdateSphere(0,0)
 
# Create model node and add to scene
modelsLogic = slicer.modules.models.logic()
model = modelsLogic.AddModel(sphere.GetOutput())
model.GetDisplayNode().SetSliceIntersectionVisibility(True)
model.GetDisplayNode().SetSliceIntersectionThickness(3)
model.GetDisplayNode().SetColor(1,1,0)
 
# Call UpdateSphere whenever the fiducials are changed
markups.AddObserver("ModifiedEvent", UpdateSphere, 2)

Add a texture mapped plane to the scene as a model

Note that model textures are not exposed in the GUI and are not saved in the scene 

# use dummy image data here
e = vtk.vtkImageEllipsoidSource()

scene = slicer.mrmlScene

# Create model node
model = slicer.vtkMRMLModelNode()
model.SetScene(scene)
model.SetName(scene.GenerateUniqueName("2DImageModel"))

planeSource = vtk.vtkPlaneSource()
model.SetAndObservePolyData(planeSource.GetOutput())

# Create display node
modelDisplay = slicer.vtkMRMLModelDisplayNode()
modelDisplay.SetColor(1,1,0) # yellow
modelDisplay.SetBackfaceCulling(0)
modelDisplay.SetScene(scene)
scene.AddNode(modelDisplay)
model.SetAndObserveDisplayNodeID(modelDisplay.GetID())

# Add to scene
modelDisplay.SetAndObserveTextureImageData(e.GetOutput())
scene.AddNode(model) 


transform = slicer.vtkMRMLLinearTransformNode()
scene.AddNode(transform) 
model.SetAndObserveTransformNodeID(transform.GetID())

vTransform = vtk.vtkTransform()
vTransform.Scale(50,50,50)
vTransform.RotateX(30)
transform.SetAndObserveMatrixTransformToParent(vTransform.GetMatrix())


Export a model to Blender, including color

plyFilePath = "/tmp/fibers.ply"

lineDisplayNode = getNode("*LineDisplay*")

tuber = vtk.vtkTubeFilter()
tuber.SetInput(lineDisplayNode.GetOutputPolyData())

tubes = tuber.GetOutput()
tubes.Update()
scalars = tubes.GetPointData().GetArray(0)
scalars.SetName("scalars")

triangles = vtk.vtkTriangleFilter()
triangles.SetInput(tubes)

colorNode = lineDisplayNode.GetColorNode()
lookupTable = vtk.vtkLookupTable()
lookupTable.DeepCopy(colorNode.GetLookupTable())
lookupTable.SetTableRange(0,1)

plyWriter = vtk.vtkPLYWriter()
plyWriter.SetInput(triangles.GetOutput())
plyWriter.SetLookupTable(lookupTable)
plyWriter.SetArrayName("scalars")

plyWriter.SetFileName(plyFilePath)
plyWriter.Write()

Clone a volume

This example shows how to clone the MRHead sample volume, including its pixel data and display settings. 

sourceVolumeNode = slicer.util.getNode('MRHead')
volumesLogic = slicer.modules.volumes.logic()
clonedVolumeNode = volumesLogic.CloneVolume(slicer.mrmlScene, sourceVolumeNode, 'Cloned volume')

Create a new volume

This example shows how to create a new empty volume. 

imageSize=[512, 512, 512]
imageSpacing=[1.0, 1.0, 1.0]
voxelType=vtk.VTK_UNSIGNED_CHAR
# Create an empty image volume
imageData=vtk.vtkImageData()
imageData.SetDimensions(imageSize)
imageData.AllocateScalars(voxelType, 1)
thresholder=vtk.vtkImageThreshold()
thresholder.SetInputData(imageData)
thresholder.SetInValue(0)
thresholder.SetOutValue(0)
# Create volume node
volumeNode=slicer.vtkMRMLScalarVolumeNode()
volumeNode.SetSpacing(imageSpacing)
volumeNode.SetImageDataConnection(thresholder.GetOutputPort())
# Add volume to scene
slicer.mrmlScene.AddNode(volumeNode)
displayNode=slicer.vtkMRMLScalarVolumeDisplayNode()
slicer.mrmlScene.AddNode(displayNode)
colorNode = slicer.util.getNode('Grey')
displayNode.SetAndObserveColorNodeID(colorNode.GetID())
volumeNode.SetAndObserveDisplayNodeID(displayNode.GetID())
volumeNode.CreateDefaultStorageNode()

Modify voxels in a volume

This example shows how to change voxels values of the MRHead sample volume. The values will be computed by function f(r,a,s,) = (r-10)*(r-10)+(a+15)*(a+15)+s*s. 

volumeNode=slicer.util.getNode('MRHead')
ijkToRas = vtk.vtkMatrix4x4()
volumeNode.GetIJKToRASMatrix(ijkToRas)
imageData=volumeNode.GetImageData()
extent = imageData.GetExtent()
for k in xrange(extent[4], extent[5]+1):
  for j in xrange(extent[2], extent[3]+1):
    for i in xrange(extent[0], extent[1]+1):
      position_Ijk=[i, j, k, 1]
      position_Ras=ijkToRas.MultiplyPoint(position_Ijk)
      r=position_Ras[0]
      a=position_Ras[1]
      s=position_Ras[2]      
      functionValue=(r-10)*(r-10)+(a+15)*(a+15)+s*s
      imageData.SetScalarComponentFromDouble(i,j,k,0,functionValue)
imageData.SetScalarComponentFromFloat(distortionVectorPosition_Ijk[0], distortionVectorPosition_Ijk[1], distortionVectorPosition_Ijk[2], 0, fillValue)
imageData.Modified()

Access values in a DTI tensor volume

This example shows how to access individual tensors at the voxel level.

First load your DWI volume and estimate tensors to produce a DTI volume called ‘Output DTI Volume’

Then open the python window: View->Python interactor

Use this command to access tensors through numpy: 

tensors = array('Output DTI Volume')

Type the following code into the Python window to access all tensor components using vtk commands: 

volumeNode=slicer.util.getNode('Output DTI Volume')
imageData=volumeNode.GetImageData()
tensors = imageData.GetPointData().GetTensors()
extent = imageData.GetExtent()
idx = 0
for k in xrange(extent[4], extent[5]+1):
  for j in xrange(extent[2], extent[3]+1):
    for i in xrange(extent[0], extent[1]+1):
      tensors.GetTuple9(idx)
      idx += 1

Change window/level (brightness/contrast) or colormap of a volume

This example shows how to change window/level of the MRHead sample volume. 

volumeNode = getNode('MRHead')
displayNode = volumeNode.GetDisplayNode()
displayNode.AutoWindowLevelOff()
displayNode.SetWindow(50)
displayNode.SetLevel(100)

Change color mapping from grayscale to rainbow: 

displayNode.SetAndObserveColorNodeID('vtkMRMLColorTableNodeRainbow')

Manipulate a Slice View

lm = slicer.app.layoutManager()
red = lm.sliceWidget('Red')
redLogic = red.sliceLogic()
# Print current slice offset position
print redLogic.GetSliceOffset()
# Change slice position
redLogic.SetSliceOffset(20)

Save a series of images from a Slice View

You can use ScreenCapture module to capture series of images. To do it programmatically, save the following into a file such as '/tmp/record.py' and then in the slicer python console type "execfile('/tmp/record.py')" 

layoutName = 'Green'
imagePathPattern = '/tmp/image-%03d.png'
steps = 10

widget = slicer.app.layoutManager().sliceWidget(layoutName)
view = widget.sliceView()
logic = widget.sliceLogic()
bounds = [0,]*6
logic.GetSliceBounds(bounds)

for step in range(steps):
    offset = bounds[4] + step/(1.*steps) * (bounds[5]-bounds[4])
    logic.SetSliceOffset(offset)
    view.forceRender()
    image = qt.QPixmap.grabWidget(view).toImage()
    image.save(imagePathPattern % step)

Save the scene into a new directory

# Create a new directory where the scene will be saved into
import time
sceneSaveDirectory = slicer.app.temporaryPath + "/saved-scene-" + time.strftime("%Y%m%d-%H%M%S")
if not os.access(sceneSaveDirectory, os.F_OK):
  os.makedirs(sceneSaveDirectory)

# Save the scene
if slicer.app.applicationLogic().SaveSceneToSlicerDataBundleDirectory(sceneSaveDirectory, None):
  logging.info("Scene saved to: {0}".format(sceneSaveDirectory))
else:
  logging.error("Scene saving failed")

Save the scene into a single MRB file

# Generate file name
import time
sceneSaveFilename = slicer.app.temporaryPath + "/saved-scene-" + time.strftime("%Y%m%d-%H%M%S") + ".mrb"

# Save scene
if slicer.util.saveScene(sceneSaveFilename):
  logging.info("Scene saved to: {0}".format(sceneSaveFilename))
else:
  logging.error("Scene saving failed")

Show a volume in the Slice Views

volumeNode = slicer.util.getNode('YourVolumeNode')
applicationLogic = slicer.app.applicationLogic()
selectionNode = applicationLogic.GetSelectionNode()
selectionNode.SetSecondaryVolumeID(volumeNode.GetID())
applicationLogic.PropagateForegroundVolumeSelection(0)

or 

n =  slicer.util.getNode('YourVolumeNode')
for color in ['Red', 'Yellow', 'Green']:
    slicer.app.layoutManager().sliceWidget(color).sliceLogic().GetSliceCompositeNode().SetForegroundVolumeID(n.GetID())

Change opacity of foreground volume in the Slice Views

lm = slicer.app.layoutManager()
sliceLogic = lm.sliceWidget('Red').sliceLogic()
compositeNode = sliceLogic.GetSliceCompositeNode()
compositeNode.SetForegroundOpacity(0.4)

Center the 3D View on the Scene

layoutManager = slicer.app.layoutManager()
threeDWidget = layoutManager.threeDWidget(0)
threeDView = threeDWidget.threeDView()
threeDView.resetFocalPoint()

Display text in a 3D view or slice view

The easiest way to show information overlaid on a viewer is to use corner annotations. 

view=slicer.app.layoutManager().threeDWidget(0).threeDView()
# Set text to "Something"
view.cornerAnnotation().SetText(vtk.vtkCornerAnnotation.UpperRight,"Something")
# Set color to red
view.cornerAnnotation().GetTextProperty().SetColor(1,0,0)
# Update the view
view.forceRender()

Turning off interpolation

You can turn off interpolation for newly loaded volumes with this script from Steve Pieper. 

def NoInterpolate(caller,event):
  for node in slicer.util.getNodes('*').values():
    if node.IsA('vtkMRMLScalarVolumeDisplayNode'):
      node.SetInterpolate(0)
	
slicer.mrmlScene.AddObserver(slicer.mrmlScene.NodeAddedEvent, NoInterpolate)

The below link explains how to put this in your startup script.

http://www.na-mic.org/Wiki/index.php/AHM2012-Slicer-Python#Refining_the_code_and_UI_with_slicerrc


Customize viewer layout

Show a custom layout of a 3D view on top of the red slice view: 

customLayout = ("<layout type=\"vertical\" split=\"true\" >"
  " <item>"
  "  <view class=\"vtkMRMLViewNode\" singletontag=\"1\">"
  "    <property name=\"viewlabel\" action=\"default\">1</property>"
  "  </view>"
  " </item>"
  " <item>"
  "  <view class=\"vtkMRMLSliceNode\" singletontag=\"Red\">"
  "   <property name=\"orientation\" action=\"default\">Axial</property>"
  "   <property name=\"viewlabel\" action=\"default\">R</property>"
  "   <property name=\"viewcolor\" action=\"default\">#F34A33</property>"
  "  </view>"
  " </item>"
  "</layout>")
  
customLayoutId=501

layoutManager = slicer.app.layoutManager()
layoutManager.layoutLogic().GetLayoutNode().AddLayoutDescription(customLayoutId, customLayout)                                         
layoutManager.setLayout(customLayoutId)

See description of standard layouts (that can be used as examples) here: https://github.com/Slicer/Slicer/blob/master/Libs/MRML/Logic/vtkMRMLLayoutLogic.cxx

Running an ITK filter in Python using SimpleITK

Open the "Sample Data" module and download "MR Head", then paste the following snippet in Python interactor: 

import SimpleITK as sitk
import sitkUtils
inputImage = sitkUtils.PullFromSlicer('MRHead')
filter = sitk.SignedMaurerDistanceMapImageFilter()
outputImage = filter.Execute(inputImage)
sitkUtils.PushToSlicer(outputImage,'outputImage')

More information:

Get current mouse coordinates in a slice view

You can get 3D (RAS) coordinates of the current mouse cursor from the crosshair singleton node as shown in the example below: 

def onMouseMoved(observer,eventid):  
  ras=[0,0,0]
  crosshairNode.GetCursorPositionRAS(ras)
  print(ras)

crosshairNode=slicer.util.getNode('Crosshair') 
crosshairNode.AddObserver(slicer.vtkMRMLCrosshairNode.CursorPositionModifiedEvent, onMouseMoved)

Thick slab reconstruction and maximum/minimum intensity volume projections

Set up 'red' slice viewer to show thick slab reconstructed from 3 slices: 

sliceNode = slicer.mrmlScene.GetNodeByID('vtkMRMLSliceNodeRed')
appLogic = slicer.app.applicationLogic()
sliceLogic = appLogic.GetSliceLogic(sliceNode)
sliceLayerLogic = sliceLogic.GetBackgroundLayer()
reslice = sliceLayerLogic.GetReslice()
reslice.SetSlabModeToMean()
reslice.SetSlabNumberOfSlices(10) # mean of 10 slices will computed
reslice.SetSlabSliceSpacingFraction(0.3) # spacing between each slice is 0.3 pixel (total 10 * 0.3 = 3 pixel neighborhood)
sliceNode.Modified()

Set up 'red' slice viewer to show maximum intensity projection (MIP): 

sliceNode = slicer.mrmlScene.GetNodeByID('vtkMRMLSliceNodeRed')
appLogic = slicer.app.applicationLogic()
sliceLogic = appLogic.GetSliceLogic(sliceNode)
sliceLayerLogic = sliceLogic.GetBackgroundLayer()
reslice = sliceLayerLogic.GetReslice()
reslice.SetSlabModeToMax()
reslice.SetSlabNumberOfSlices(600) # use a large number of slices (600) to cover the entire volume
reslice.SetSlabSliceSpacingFraction(0.5) # spacing between slices are 0.5 pixel (supersampling is useful to reduce interpolation artifacts)
sliceNode.Modified()

The projected image is available in a vtkImageData object by calling reslice.GetOutput().

Change default file type for nodes (that have never been saved yet)

Default node can be specified that will be used as a basis of all new storage nodes. This can be used for setting default file extension. For example, change file format to STL for model nodes: 

msn=slicer.vtkMRMLModelStorageNode()
msn.SetDefaultWriteFileExtension('stl')
slicer.mrmlScene.AddDefaultNode(msn)

Change file type for saving for all volumes (with already existing storage nodes)

requiredFileExtension = '.nia'
originalFileExtension = '.nrrd'
volumeNodes = slicer.mrmlScene.GetNodesByClass('vtkMRMLScalarVolumeNode')
volumeNodes.UnRegister(slicer.mrmlScene)
volumeNodes.InitTraversal()
volumeNode = volumeNodes.GetNextItemAsObject()
while volumeNode:
  volumeStorageNode = volumeNode.GetStorageNode()
  if not volumeStorageNode:
    volumeStorageNode = volumeNode.CreateDefaultStorageNode()
    slicer.mrmlScene.AddNode(volumeStorageNode)
    volumeStorageNode.UnRegister(None)
    volumeNode.SetAndObserveStorageNodeID(volumeStorageNode.GetID())
    volumeStorageNode.SetFileName(volumeNode.GetName()+requiredFileExtension)
  else:
    volumeStorageNode.SetFileName(volumeStorageNode.GetFileName().replace(originalFileExtension,requiredFileExtension))
  volumeNode = volumeNodes.GetNextItemAsObject()

Segmentations

For all operations accessing or manupilating the internals of a segmentation will need this import! 

import vtkSegmentationCorePython as vtkSegmentationCore

Get a segment

segmentation = segmentationNode.GetSegmentation()
segment = segmentation.GetSegment(segmentID)

Get a representation of a segment

Get binary labelmap, if it does not exist, it will return None: 

image = segmentationNode.GetBinaryLabelmapRepresentation(segmentID)

Get closed surface, if it does not exist, it will return None: 

polydata = segmentationNode.GetClosedSurfaceRepresentation(segmentID)

Get binary labelmap. If it does not exist then it will be created for that single segment. Applies parent transforms by default (if not desired, another argument needs to be added to the end: false): 

outputOrientedImageData = vtkSegmentationCore.vtkOrientedImageData()
slicer.vtkSlicerSegmentationsModuleLogic.GetSegmentBinaryLabelmapRepresentation(segmentationNode, segmentID, outputOrientedImageData) # Get labelmap

Get any representation (example is shown for closed surface). If it does not exist then it will be created for that single segment. Applies parent transforms by default (if not desired, another argument needs to be added to the end: false): 

outputPolyData = vtk.vtkPolyData()
slicer.vtkSlicerSegmentationsModuleLogic.GetSegmentRepresentation(segmentationNode, segmentID, vtkSegmentationCore.vtkSegmentationConverter.GetSegmentationClosedSurfaceRepresentationName(), outputPolyData)

Convert all segments using default path and conversion parameters

segmentation.CreateRepresentation(vtkSegmentationCore.vtkSegmentationConverter.GetSegmentationBinaryLabelmapRepresentationName()) # This creates binary labelmap, but same idea for all others

Convert all segments using custom path or conversion parameters

referenceGeometry = vtkSegmentationCore.vtkSegmentationConverter.SerializeImageGeometry(referenceImageData)
segmentation.SetConversionParameter(vtkSegmentationCore.vtkSegmentationConverter.GetReferenceImageGeometryParameterName(), referenceGeometry)

Re-convert using a modified conversion parameter

import vtkSegmentationCorePython as vtkSegmentationCore
segmentation = getNode('Segmentation').GetSegmentation()

# Turn of surface smoothing
segmentation.SetConversionParameter('Smoothing factor','0.0')

# Recreate representation using modified parameters (and default conversion path)
segmentation.RemoveRepresentation(vtkSegmentationCore.vtkSegmentationConverter.GetSegmentationClosedSurfaceRepresentationName())
segmentation.CreateRepresentation(vtkSegmentationCore.vtkSegmentationConverter.GetSegmentationClosedSurfaceRepresentationName())

How to run segment editor effects from a script

Editor effects are complex because they need to handle changing master volumes, undo/redo, masking operations, etc. Therefore, instead of using a segment editor effect, it is simpler to run the underlying filters directly from script.

This example demonstrates how to perform auto-complete by growing from seeds (grow-cut segmentation) without GUI:

https://subversion.assembla.com/svn/slicerrt/trunk/SlicerRt/samples/PythonScripts/SegmentGrowCut/SegmentGrowCut.py

Subject hierarchy

Get the pseudo-singleton subject hierarchy node

It manages the whole hierarchy and provides functions to access and manipulate 

 shNode = slicer.vtkMRMLSubjectHierarchyNode.GetSubjectHierarchyNode(slicer.mrmlScene)

Create subject hierarchy item

 # If it is for a data node, it is automatically created, but the create function can be used to set parent:
 shNode.CreateItem(parentItemID, dataNode)
 # If it is a hierarchy item without a data node, then the create function must be used:
 shNode.CreateSubjectItem(parentItemID, name)
 shNode.CreateFolderItem(parentItemID, name)
 shNode.CreateHierarchyItem(parentItemID, name, level) # Advanced method to set level attribute manually (usually subject, study, or folder, but it can be a virtual branch for example)

Get subject hierarchy item

Items in subject hierarchy are uniquely identified by integer IDs 

 # Get scene item ID first because it is the root item:
 sceneItemID = shNode.GetSceneItemID()
 # Get direct child by name
 subjectItemID = shNode.GetItemChildWithName(sceneItemID, 'Subject_1')
 # Get item for data node
 itemID = shNode.GetItemByDataNode(dataNode)
 # Get item by UID (such as DICOM)
 itemID = shNode.GetItemByUID(slicer.vtkMRMLSubjectHierarchyConstants.GetDICOMUIDName(), seriesInstanceUid)
 itemID = shNode.GetItemByUIDList(slicer.vtkMRMLSubjectHierarchyConstants.GetDICOMInstanceUIDName(), instanceUID)
 # Invalid item ID for checking validity of a given ID (most functions return the invalid ID when item is not found)
 invalidItemID = slicer.vtkMRMLSubjectHierarchyNode.GetInvalidItemID()

Traverse children of a subject hierarchy item

 children = vtk.vtkIdList()
 shNode.GetItemChildren(parent, children)
 for i in xrange(children.GetNumberOfIds()):
   child = children.GetId(i)
   ...

Manipulate subject hierarchy item

Instead of node operations on the individual subject hierarchy nodes, item operations are performed on the one subject hierarchy node. 

 # Set item name
 shNode.SetItemName(itemID, 'NewName')
 # Set item parent (reparent)
 shNode.SetItemParent(itemID, newParentItemID)
 # Set visibility of data nodes associated to items in a branch (or a leaf item)
 shNode.SetDisplayVisibilityForBranch(itemID, 1)
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