test len instead of comparing to empty list

logmetric.py

@@ -139,7 +139,7 @@ class LogMetric(evaluate.Metric):
             if P == 0 and R == 0: return 1.0      # since this leads to (|R| + |P|) = 0
             return 1 - (np.sum(np.abs(R - P) / (np.abs(R) + np.abs(P))))    # (n = 1)
         else:
-            if P == [] and R == []: return 1.0     # since this leads to n = 0
+            if len(P) == 0 and len(R) == 0: return 1.0     # since this leads to n = 0
             n = len(P)
             P = np.array(P)
             R = np.array(R)