It is often usefull to select cells by their type for visualization in Paraview. Visualizing boundary layer meshes for example or extracting the surface elements of a mesh can be done by using the following script in the Programmable filter of Paraview.
input = self.GetUnstructuredGridInput()
output = self.GetUnstructuredGridOutput();
# copy all curent data
output.GetPointData().PassData(input.GetPointData())
output.GetCellData().PassData(input.GetCellData())
# create an array holding the VTK cell type id of each element
cellTypes = vtk.vtkUnsignedCharArray()
cellTypes.DeepCopy(input.GetCellTypesArray())
cellTypes.SetName("Cell Types")
output.GetCellData().AddArray(cellTypes)
Even simpler you can import this file (export_cell_types.cpd) from the menu Tools>Manage Custom Filters… > Import.
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