diff --git a/dpdata/abacus/relax.py b/dpdata/abacus/relax.py
index cce64b853..1ba975edd 100644
--- a/dpdata/abacus/relax.py
+++ b/dpdata/abacus/relax.py
@@ -157,7 +157,7 @@ def get_coords_from_log(loglines, natoms):
     # transfer bohrium to angstrom
     cells *= bohr2ang
     coords *= bohr2ang
-    
+
     if len(stress) > 0:
         virial = np.zeros([len(cells), 3, 3])
         for i in range(len(cells)):
@@ -206,7 +206,7 @@ def get_frame(fname):
     data["coords"] = coords
     data["energies"] = energy
     data["forces"] = force
-    if virial != None:
+    if virial is not None:
         data["virials"] = virial
     data["stress"] = stress
     data["orig"] = np.zeros(3)