Fix the number of samples returned for the interpolation routines (#23 …

…| GRIDEDIT-744)

meshkernel/meshkernel.py

@@ -1432,8 +1432,7 @@ def mesh2d_triangulation_interpolation(
         """
         c_samples = CGeometryList.from_geometrylist(samples)
 
-        number_of_coordinates = c_samples.n_coordinates
-
+        number_of_coordinates = self._get_num_coordinates(location_type)
         x_coordinates = np.empty(number_of_coordinates, dtype=np.double)
         y_coordinates = np.empty(number_of_coordinates, dtype=np.double)
         values = np.empty(number_of_coordinates, dtype=np.double)
@@ -1474,8 +1473,7 @@ def mesh2d_averaging_interpolation(
         """
         c_samples = CGeometryList.from_geometrylist(samples)
 
-        number_of_coordinates = c_samples.n_coordinates
-
+        number_of_coordinates = self._get_num_coordinates(location_type)
         x_coordinates = np.empty(number_of_coordinates, dtype=np.double)
         y_coordinates = np.empty(number_of_coordinates, dtype=np.double)
         values = np.empty(number_of_coordinates, dtype=np.double)
@@ -2215,3 +2213,26 @@ def curvilinear_delete_node(self, x_coordinate: float, y_coordinate: float) -> N
             c_double(x_coordinate),
             c_double(y_coordinate),
         )
+
+    def _get_num_coordinates(self, location_type):
+        """Get the numbers of mesh coordinates of a specific location.
+
+        Args:
+            location_type (Mesh2dLocation): The location type.
+
+        Raises:
+            Exception: This exception gets raised if an invalid location is used.
+        """
+
+        mesh = self.mesh2d_get()
+
+        if location_type == Mesh2dLocation.NODES:
+            number_of_coordinates = len(mesh.node_x)
+        elif location_type == Mesh2dLocation.FACES:
+            number_of_coordinates = len(mesh.face_x)
+        elif location_type == Mesh2dLocation.EDGES:
+            number_of_coordinates = len(mesh.edge_x)
+        else:
+            raise Exception("wrong location_type")
+
+        return number_of_coordinates