Error handling

Author: jorgensd

src/festim/hydrogen_transport_problem.py

@@ -452,7 +452,7 @@ def initialise_exports(self):
                 if self.mesh.coordinate_system != CoordinateSystem.CARTESIAN:
                     raise NotImplementedError(
                         f"Derived quantity exports are not implemented for "
-                        f"{self.mesh.coordinate_system} meshes"
+                        f"{str(self.mesh.coordinate_system)} meshes"
                     )
 
             # if name of species is given then replace with species object

src/festim/mesh/mesh.py

@@ -29,6 +29,16 @@ def from_string(cls, s: str):
                 "coordinate_system must be one of 'cartesian', 'cylindrical', or 'spherical'"
             )
 
+    def __str__(self):
+        if self == CoordinateSystem.CARTESIAN:
+            return "cartesian"
+        elif self == CoordinateSystem.CYLINDRICAL:
+            return "cylindrical"
+        elif self == CoordinateSystem.SPHERICAL:
+            return "spherical"
+        else:
+            raise ValueError("Invalid CoordinateSystem value")
+
 
 class Mesh:
     """