add XDMF to VTU converter

- simplifies comparisons (ASCII)

cpppetsc/tools/convert_xdmf_to_vtu.py

+#!/usr/bin/env python3
+
+# © 2022 ETH Zurich, Mechanics and Materials Lab
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Converts an XDMF file to an ASCII VTU file.
+"""
+
+from vtk import vtkXMLUnstructuredGridWriter, vtkXdmfReader
+import argparse
+import pathlib
+
+
+def parse_input_filename() -> pathlib.Path:
+    """
+    Parses the command line parameters and returns the input file name.
+    """
+    parser = argparse.ArgumentParser(
+        description="Converts an XDMF file to an ASCII VTU file."
+    )
+    parser.add_argument("input", help="*.xdmf file to read", type=pathlib.Path)
+    return parser.parse_args().input
+
+
+def main():
+    """
+    Reads the XDMF file from the path provided via command line argument
+    and writes an ASCII VTU file to the same location, but with extension ".vtu".
+    """
+    input = parse_input_filename()
+    output = input.stem + ".vtu"
+
+    reader = vtkXdmfReader()
+    reader.SetFileName(input)
+    reader.Update()
+    writer = vtkXMLUnstructuredGridWriter()
+    writer.SetFileName(output)
+    writer.SetDataModeToAscii()
+    writer.SetInputData(reader.GetOutput())
+    writer.Write()
+
+
+if __name__ == "__main__":
+    main()