diff --git a/setup.cfg b/setup.cfg
index 488fb1189..ba6c23d2d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = meshio
-version = 5.2.2
+version = 5.2.3
 author = Nico Schlömer et al.
 author_email = nico.schloemer@gmail.com
 description = I/O for many mesh formats
diff --git a/src/meshio/_cli/_main.py b/src/meshio/_cli/_main.py
index 05645cfd2..d2f06a18a 100644
--- a/src/meshio/_cli/_main.py
+++ b/src/meshio/_cli/_main.py
@@ -24,7 +24,6 @@ def main(argv=None):
     )
 
     parser = subparsers.add_parser("convert", help="Convert mesh files", aliases=["c"])
-
     _convert.add_args(parser)
     parser.set_defaults(func=_convert.convert)
 
diff --git a/src/meshio/ansys/_ansys.py b/src/meshio/ansys/_ansys.py
index fce68d522..c52716f50 100644
--- a/src/meshio/ansys/_ansys.py
+++ b/src/meshio/ansys/_ansys.py
@@ -365,15 +365,14 @@ def read(filename):  # noqa: C901
                 obj = re.match("\\(45 \\([0-9]+ ([\\S]+) ([\\S]+)\\)\\(\\)\\)", line)
                 if obj:
                     warn(
-                        "Zone specification not supported yet (%r, %r). " "Skipping.",
-                        obj.group(1),
-                        obj.group(2),
+                        f"Zone specification not supported yet ({obj.group(1)}, {obj.group(2)}). "
+                        + "Skipping.",
                     )
                 else:
                     warn("Zone specification not supported yet.")
 
             else:
-                warn("Unknown index %r. Skipping.", index)
+                warn(f"Unknown index {index}. Skipping.")
                 # Skipping ahead to the next line with two closing brackets.
                 _skip_close(f, line.count("(") - line.count(")"))
 
diff --git a/src/meshio/dolfin/_dolfin.py b/src/meshio/dolfin/_dolfin.py
index f26b22214..b9af20476 100644
--- a/src/meshio/dolfin/_dolfin.py
+++ b/src/meshio/dolfin/_dolfin.py
@@ -71,7 +71,7 @@ def _read_mesh(filename):
             assert cell_tags is not None
             cells[0][1][k] = [elem.attrib[t] for t in cell_tags]
         else:
-            warn("Unknown entry %s. Ignoring.", elem.tag)
+            warn(f"Unknown entry {elem.tag}. Ignoring.")
 
         elem.clear()
 
@@ -140,9 +140,7 @@ def _write_mesh(filename, points, cell_type, cells):
         discarded_cell_types = {c.type for c in cells if c.type != cell_type}
         warn(
             "DOLFIN XML can only handle one cell type at a time. "
-            "Using %s, discarding %s.",
-            cell_type,
-            ", ".join(discarded_cell_types),
+            + f"Using {cell_type}, discarding {', '.join(discarded_cell_types)}.",
         )
 
     dim = points.shape[1]
diff --git a/src/meshio/vtk/_vtk_42.py b/src/meshio/vtk/_vtk_42.py
index 8462d856e..4f23c9c94 100644
--- a/src/meshio/vtk/_vtk_42.py
+++ b/src/meshio/vtk/_vtk_42.py
@@ -605,7 +605,7 @@ def pad(array):
     if mesh.points.shape[1] == 2:
         warn(
             "VTK requires 3D points, but 2D points given. "
-            "Appending 0 third component."
+            + "Appending 0 third component."
         )
         points = pad(mesh.points)
     else:
@@ -616,7 +616,7 @@ def pad(array):
             if len(values.shape) == 2 and values.shape[1] == 2:
                 warn(
                     "VTK requires 3D vectors, but 2D vectors given. "
-                    "Appending 0 third component to {}.".format(name)
+                    + f"Appending 0 third component to {name}."
                 )
                 mesh.point_data[name] = pad(values)
 
@@ -625,7 +625,7 @@ def pad(array):
             if len(values.shape) == 2 and values.shape[1] == 2:
                 warn(
                     "VTK requires 3D vectors, but 2D vectors given. "
-                    "Appending 0 third component to {}.".format(name)
+                    + f"Appending 0 third component to {name}."
                 )
                 data[k] = pad(data[k])
 
diff --git a/src/meshio/xdmf/time_series.py b/src/meshio/xdmf/time_series.py
index 0bf2a5d8b..a3f85030a 100644
--- a/src/meshio/xdmf/time_series.py
+++ b/src/meshio/xdmf/time_series.py
@@ -256,7 +256,7 @@ def __init__(self, filename, data_format: str = "HDF") -> None:
         ET.register_namespace("xi", "https://www.w3.org/2001/XInclude/")
 
         self.has_mesh = False
-        self.mesh_name = None
+        self.mesh_name = "mesh"
 
     def __enter__(self):
         if self.data_format == "HDF":
@@ -284,7 +284,6 @@ def write_points_cells(
         #     <DataItem Dimensions="8457 2" Format="HDF">maxwell.h5:/Mesh/0/mesh/geometry</DataItem>
         #   </Geometry>
         # </Grid>
-        self.mesh_name = "mesh"
         grid = ET.SubElement(
             self.domain, "Grid", Name=self.mesh_name, GridType="Uniform"
         )
@@ -388,18 +387,17 @@ def cells(
                 NumberOfElements=str(num_cells),
             )
             dt, prec = numpy_to_xdmf_dtype[cell_blocks[0].data.dtype.name]
-            dim = "{} {}".format(*cell_blocks[0].data.shape)
             data_item = ET.SubElement(
                 topo,
                 "DataItem",
                 DataType=dt,
-                Dimensions=dim,
+                Dimensions="{} {}".format(*cell_blocks[0].data.shape),
                 Format=self.data_format,
                 Precision=prec,
             )
             data_item.text = self.numpy_to_xml_string(cell_blocks[0].data)
         elif len(cell_blocks) > 1:
-            total_num_cells = sum(c.data.shape[0] for c in cell_blocks)
+            total_num_cells = sum(len(c.data) for c in cell_blocks)
             topo = ET.SubElement(
                 grid,
                 "Topology",