diff --git a/openmc/universe.py b/openmc/universe.py
index db0d55f21d..bdd6e6ec98 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -469,7 +469,7 @@ class Universe(UniverseBase):
         """
         nuclides = OrderedDict()
 
-        if len(self._atoms) > 0:
+        if self._atoms:
             volume = self.volume
             for name, atoms in self._atoms.items():
                 nuclide = openmc.Nuclide(name)
diff --git a/tests/unit_tests/test_universe.py b/tests/unit_tests/test_universe.py
index 6f4177f54c..33c86b1506 100644
--- a/tests/unit_tests/test_universe.py
+++ b/tests/unit_tests/test_universe.py
@@ -139,7 +139,7 @@ def test_get_nuclide_densities():
     material = openmc.Material()
     material.add_elements_from_formula("H2O")
     material.set_density("g/cm3", 1)
-    cell = openmc.Cell(region=-surf,fill=material)
+    cell = openmc.Cell(region=-surf, fill=material)
     universe = openmc.Universe(cells=[cell])
     with pytest.raises(RuntimeError):
         universe.get_nuclide_densities()