SegmentStatistics error in Python

Hi. I have a bunch of segments in an RTStruct file, and a bunch of images that I want to get some statistics from. Doing this manually is a bit of a timehog, so I looked into writing a quick python script and running it using the python interactor. It’s based largely on things I found on this forum and Google, so could be very wrong, but at the moment it seems to pull through the correct segments and scalars, and generates a data table, just doesn’t populate it.

At the moment, I get an error that

if not segmentationNode.GetParentTransformNode() is None:
AttributeError: 'NoneType' object has no attribute 'GetParentTransformNode'

My code is below:

print("Starting scalar volume processing loop...")
import SegmentStatistics

rtstruct_node = slicer.util.getFirstNodeByName("RTSTRUCT") #get the RTStruct Node
scalar_volume_nodes = slicer.util.getNodesByClass("vtkMRMLScalarVolumeNode") #retrieve all scalar nodes

for scalar_volume_node in scalar_volume_nodes:
    if 'Dose' in scalar_volume_node.GetName(): #check if dose is in the name, as don't want to analysis the CT etc.
        scalar_volume_name = scalar_volume_node.GetName() #Get the unique name for the scalar volume
        print("Quantifying node " + scalar_volume_name)
        statistics_table_node = slicer.mrmlScene.AddNewNodeByClass("vtkMRMLTableNode", scalar_volume_name + "_stat") #Create a new table node to hold the statistics

        for segment_index in range(rtstruct_node.GetSegmentation().GetNumberOfSegments()): #Loop through the segments and compute statistics for each segment
            segment_name = rtstruct_node.GetSegmentation().GetNthSegment(segment_index).GetName()
            segment_id = rtstruct_node.GetSegmentation().GetNthSegmentID(segment_index)
            print("Measuring segment " + segment_name + " with ID: " + segment_id)
            segmentStat = SegmentStatistics.SegmentStatisticsLogic()
            segmentStat.getParameterNode().SetParameter("Segmentation", segment_id)
            segmentStat.getParameterNode().SetParameter("ScalarVolume", scalar_volume_node.GetID())

Any help would be greatly appreciated! There aren’t many online resources (that I’ve found) and it is quite the learning curve.

Can you show the code where segmentationNode is defined?
You will get this error if segmentationNode is equal to None and therefore has no attributes.

Ah, that is the entirety of the code I have, and that might be the issue. The segments are in the rtstruct file, so I thought slicer.util.getFirstNodeByName(“RTSTRUCT”) would retrieve this as the segmentation. As the print statements provided the right information back to me, I didn’t question this.

Do I need to change the first line in rtstruct_node to something like
restruct_node = slicer.util.getNodesByClass("vtkMRMLSegmentationNode")

I’m away from my computer at the moment to try this, but will give it a go later today.

Thank you