diff --git a/scripts/openmc-voxel-to-vtk b/scripts/openmc-voxel-to-vtk
index 33251144f..01b4808d2 100755
--- a/scripts/openmc-voxel-to-vtk
+++ b/scripts/openmc-voxel-to-vtk
@@ -1,54 +1,46 @@
 #!/usr/bin/env python3
 
-import struct
-import sys
 from argparse import ArgumentParser
 
-import numpy as np
 import h5py
 import vtk
 
 _min_version = (2, 0)
 
 
-def main():
-    # Process command line arguments
-    parser = ArgumentParser()
-    parser.add_argument('voxel_file', help='Path to voxel file')
-    parser.add_argument('-o', '--output', action='store',
-                        default='plot', help='Path to output VTK file.')
-    args = parser.parse_args()
+def voxel_to_vtk(voxel_file: str, output: str):
 
     # Read data from voxel file
-    fh = h5py.File(args.voxel_file, 'r')
+    fh = h5py.File(voxel_file, "r")
 
     # check version
-    version = tuple(fh.attrs['version'])
+    version = tuple(fh.attrs["version"])
     if version < _min_version:
-        old_version = ".".join(map(str,version))
-        min_version = ".".join(map(str,_min_version))
-        err_msg = "This voxel file's version is {}. This script " \
-                  "only supports voxel files with version {} or " \
-                  "higher. Please generate a new voxel file using " \
-                  "a newer version of OpenMC.".format(old_version, min_version)
+        old_version = ".".join(map(str, version))
+        min_version = ".".join(map(str, _min_version))
+        err_msg = (
+            "This voxel file's version is {}. This script "
+            "only supports voxel files with version {} or "
+            "higher. Please generate a new voxel file using "
+            "a newer version of OpenMC.".format(old_version, min_version)
+        )
         raise ValueError(err_msg)
 
-    dimension = fh.attrs['num_voxels']
-    width = fh.attrs['voxel_width']
-    lower_left = fh.attrs['lower_left']
+    dimension = fh.attrs["num_voxels"]
+    width = fh.attrs["voxel_width"]
+    lower_left = fh.attrs["lower_left"]
 
     nx, ny, nz = dimension
-    upper_right = lower_left + width*dimension
 
     grid = vtk.vtkImageData()
-    grid.SetDimensions(nx+1, ny+1, nz+1)
+    grid.SetDimensions(nx + 1, ny + 1, nz + 1)
     grid.SetOrigin(*lower_left)
     grid.SetSpacing(*width)
 
     # transpose data from OpenMC ordering (zyx) to VTK ordering (xyz)
     # and flatten to 1-D array
     print("Reading and translating data...")
-    h5data = fh['data'][...]
+    h5data = fh["data"][...]
 
     data = vtk.vtkIntArray()
     data.SetName("id")
@@ -62,11 +54,23 @@ def main():
         writer.SetInputData(grid)
     else:
         writer.SetInput(grid)
-    if not args.output.endswith(".vti"):
-        args.output += ".vti"
-    writer.SetFileName(args.output)
-    print("Writing VTK file {}...".format(args.output))
+    if not output.endswith(".vti"):
+        output += ".vti"
+    writer.SetFileName(output)
+    print("Writing VTK file {}...".format(output))
     writer.Write()
 
-if __name__ == '__main__':
-    main()
+
+if __name__ == "__main__":
+    # Process command line arguments
+    parser = ArgumentParser('Converts a voxel HDF5 file to a VTK file')
+    parser.add_argument("voxel_file", help="Path to voxel h5 file")
+    parser.add_argument(
+        "-o",
+        "--output",
+        action="store",
+        default="plot",
+        help="Path to output VTK file.",
+    )
+    args = parser.parse_args()
+    voxel_to_vtk(args.voxel_file, args.output)