diff --git a/pydmd/dmdbase.py b/pydmd/dmdbase.py
index 17f3662..778a6b8 100644
--- a/pydmd/dmdbase.py
+++ b/pydmd/dmdbase.py
@@ -201,7 +201,7 @@ class DMDBase(object):
         else:
             input_shapes = [np.asarray(x).shape for x in X]
 
-            if len(set(input_shapes)) is not 1:
+            if len(set(input_shapes)) != 1:
                 raise ValueError('Snapshots have not the same dimension.')
 
             snapshots_shape = input_shapes[0]
@@ -235,7 +235,7 @@ class DMDBase(object):
         https://arxiv.org/pdf/1502.03854.pdf
         """
         # Do not perform tlsq
-        if tlsq_rank is 0:
+        if tlsq_rank == 0:
             return X, Y
 
         V = np.linalg.svd(np.append(X, Y, axis=0), full_matrices=False)[-1]
@@ -269,7 +269,7 @@ class DMDBase(object):
         U, s, V = np.linalg.svd(X, full_matrices=False)
         V = V.conj().T
 
-        if svd_rank is 0:
+        if svd_rank == 0:
             omega = lambda x: 0.56 * x ** 3 - 0.95 * x ** 2 + 1.82 * x + 1.43
             beta = np.divide(*sorted(X.shape))
             tau = np.median(s) * omega(beta)