diff --git a/reconstructSPI/iterative_refinement/expectation_maximization.py b/reconstructSPI/iterative_refinement/expectation_maximization.py
index ae7d57e..fecb13d 100644
--- a/reconstructSPI/iterative_refinement/expectation_maximization.py
+++ b/reconstructSPI/iterative_refinement/expectation_maximization.py
@@ -204,7 +204,7 @@ def normalize_map(map_3d, counts, norm_const):
             Shape (n_pix, n_pix, n_pix)
             map normalized by counts.
         """
-        return map_3d * counts / (norm_const + counts ** 2)
+        return map_3d * counts / (norm_const + counts**2)
 
     @staticmethod
     def apply_noise_model(map_3d_f_norm_1, map_3d_f_norm_2):
@@ -359,7 +359,7 @@ def generate_slices(map_3d_f, xy_plane, n_pix, rots):
         map_3d_f = np.ones_like(map_3d_f)
         xyz_rotated = np.ones_like(xy_plane)
 
-        size = n_rotations * n_pix ** 2
+        size = n_rotations * n_pix**2
         slices = np.random.normal(size=size)
         slices = slices.reshape((n_rotations, n_pix, n_pix))
         return slices, xyz_rotated
diff --git a/tests/test_expectation_maximization.py b/tests/test_expectation_maximization.py
index 4f44da6..37ee222 100644
--- a/tests/test_expectation_maximization.py
+++ b/tests/test_expectation_maximization.py
@@ -90,7 +90,7 @@ def test_grid_SO3_uniform(test_ir, n_particles):
 def test_generate_xy_plane(test_ir, n_pix):
     """Test generation of xy plane."""
     xy_plane = test_ir.generate_xy_plane(n_pix)
-    assert xy_plane.shape == (n_pix ** 2, 3)
+    assert xy_plane.shape == (n_pix**2, 3)
 
 
 def test_generate_slices(test_ir, n_particles, n_pix):
@@ -101,9 +101,9 @@ def test_generate_slices(test_ir, n_particles, n_pix):
 
     slices, xyz_rotated = test_ir.generate_slices(map_3d, xy_plane, n_pix, rots)
 
-    assert xy_plane.shape == (n_pix ** 2, 3)
+    assert xy_plane.shape == (n_pix**2, 3)
     assert slices.shape == (n_particles, n_pix, n_pix)
-    assert xyz_rotated.shape == (n_pix ** 2, 3)
+    assert xyz_rotated.shape == (n_pix**2, 3)
 
 
 def test_apply_ctf_to_slice(test_ir, n_pix):