diff --git a/gprMax/materials.py b/gprMax/materials.py
index 51f5fb8b..95e07ba1 100644
--- a/gprMax/materials.py
+++ b/gprMax/materials.py
@@ -249,12 +249,13 @@ def process_materials(G):
                 z += 3
 
         # Construct information on material properties for printing table
-        materialtext = []
-        materialtext.append(str(material.numID))
-        materialtext.append(material.ID[:50] if len(material.ID) > 50 else material.ID)
-        materialtext.append(material.type)
-        materialtext.append(f'{material.er:g}')
-        materialtext.append(f'{material.se:g}')
+        materialtext = [
+            str(material.numID),
+            material.ID[:50] if len(material.ID) > 50 else material.ID,
+            material.type,
+            f'{material.er:g}',
+            f'{material.se:g}',
+        ]
         if config.get_model_config().materials['maxpoles'] > 0:
             if 'debye' in material.type:
                 materialtext.append('\n'.join('{:g}'.format(deltaer) for deltaer in material.deltaer))
@@ -274,9 +275,9 @@ def process_materials(G):
             else:
                 materialtext.extend(['', '', '', '', ''])
 
-        materialtext.append(f'{material.mr:g}')
-        materialtext.append(f'{material.sm:g}')
-        materialtext.append(material.averagable)
+        materialtext.extend(
+            (f'{material.mr:g}', f'{material.sm:g}', material.averagable)
+        )
         materialsdata.append(materialtext)
 
     return materialsdata
diff --git a/gprMax/user_inputs.py b/gprMax/user_inputs.py
index 096ed74d..c920f5e7 100644
--- a/gprMax/user_inputs.py
+++ b/gprMax/user_inputs.py
@@ -65,7 +65,7 @@ class UserInput:
         except ValueError as err:
             v = ['x', 'y', 'z']
             # Discretisation
-            dl = getattr(self.grid, 'd' + err.args[0])
+            dl = getattr(self.grid, f'd{err.args[0]}')
             # Incorrect index
             i = p[v.index(err.args[0])]
             if name:
diff --git a/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate.py b/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate.py
index 9e080890..eda4698f 100755
--- a/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate.py
+++ b/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate.py
@@ -29,10 +29,20 @@ rx = gprMax.Rx(p1=(0.038, 0.114, 0.013))
 plate = gprMax.Plate(p1=(0.013, 0.013, 0.013), 
                      p2=(0.038, 0.113, 0.013), material_id='pec')
 
-gv1 = gprMax.GeometryView(p1=(0, 0, 0), p2=(x, y, z), dl=(dl, dl, dl),
-                          filename=Path(*parts[:-1], parts[-1] + '_n'), output_type='n')
-gv2 = gprMax.GeometryView(p1=(0, 0, 0), p2=(x, y, z), dl=(dl, dl, dl),
-                          filename=Path(*parts[:-1], parts[-1] + '_f'), output_type='f')
+gv1 = gprMax.GeometryView(
+    p1=(0, 0, 0),
+    p2=(x, y, z),
+    dl=(dl, dl, dl),
+    filename=Path(*parts[:-1], f'{parts[-1]}_n'),
+    output_type='n',
+)
+gv2 = gprMax.GeometryView(
+    p1=(0, 0, 0),
+    p2=(x, y, z),
+    dl=(dl, dl, dl),
+    filename=Path(*parts[:-1], f'{parts[-1]}_f'),
+    output_type='f',
+)
 
 pmls = {'CFS-PML': {'pml': gprMax.PMLProps(formulation='HORIPML', thickness=10),
                     # Parameters from http://dx.doi.org/10.1109/TAP.2018.2823864
diff --git a/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate_ref.py b/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate_ref.py
index 1b0c8d85..c1a717c0 100755
--- a/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate_ref.py
+++ b/testing/models_pmls/pml_3D_pec_plate/pml_3D_pec_plate_ref.py
@@ -29,10 +29,20 @@ rx = gprMax.Rx(p1=(0.113, 0.189, 0.088))
 plate = gprMax.Plate(p1=(0.088, 0.088, 0.088), 
                      p2=(0.113, 0.188, 0.088), material_id='pec')
 
-gv1 = gprMax.GeometryView(p1=(0, 0, 0), p2=(x, y, z), dl=(dl, dl, dl),
-                          filename=Path(*parts[:-1], parts[-1] + '_n'), output_type='n')
-gv2 = gprMax.GeometryView(p1=(0, 0, 0), p2=(x, y, z), dl=(dl, dl, dl),
-                          filename=Path(*parts[:-1], parts[-1] + '_f'), output_type='f')
+gv1 = gprMax.GeometryView(
+    p1=(0, 0, 0),
+    p2=(x, y, z),
+    dl=(dl, dl, dl),
+    filename=Path(*parts[:-1], f'{parts[-1]}_n'),
+    output_type='n',
+)
+gv2 = gprMax.GeometryView(
+    p1=(0, 0, 0),
+    p2=(x, y, z),
+    dl=(dl, dl, dl),
+    filename=Path(*parts[:-1], f'{parts[-1]}_f'),
+    output_type='f',
+)
 
 pml = gprMax.PMLProps(formulation='HORIPML', thickness=10)