better string formatting

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>

Author: kkiesling

openmc_plotter/main_window.py

@@ -1232,20 +1232,20 @@ def viewMaterialProps(self, id):
         """display material properties in message box"""
         mat = openmc.lib.materials[id]
         if mat.name:
-            msg_str = "Material {} ({}) Properties\n\n".format(id, mat.name)
+            msg_str = f"Material {id} ({mat.name}) Properties\n\n"
         else:
-            msg_str = "Material {} Properties\n\n".format(id)
+            msg_str = f"Material {id} Properties\n\n"
 
         # get density and temperature
         dens_g = mat.get_density(units='g/cm3')
         dens_a = mat.get_density(units='atom/b-cm')
-        msg_str += "Density: {:.3f} g/cm3 ({:.3e} atom/b-cm)\n".format(dens_g, dens_a)
-        msg_str += "Temperature: {} K\n\n".format(mat.temperature)
+        msg_str += f"Density: {dens_g:.3f} g/cm3 ({dens_a:.3e} atom/b-cm)\n"
+        msg_str += f"Temperature: {mat.temperature} K\n\n"
 
         # get nuclides and their densities
         msg_str += "Nuclide densities [atom/b-cm]:\n"
         for nuc, dens in zip(mat.nuclides, mat.densities):
-            msg_str += '{}: {:5.3e}\n'.format(nuc, dens)
+            msg_str += f'{nuc}: {dens:5.3e}\n'
 
         msg_box = QMessageBox()
         msg_box.setText(msg_str)