diff --git a/dislib/commons/rf/data.py b/dislib/commons/rf/data.py
index 8e4bf546..e5155bdc 100644
--- a/dislib/commons/rf/data.py
+++ b/dislib/commons/rf/data.py
@@ -412,7 +412,7 @@ def _fill_samples_file(samples_path, row_blocks, start_idx):
     rows_samples = Array._merge_blocks(row_blocks)
     rows_samples = rows_samples.astype(dtype="float32", casting="same_kind")
     samples = np.lib.format.open_memmap(samples_path, mode="r+")
-    samples[start_idx : start_idx + rows_samples.shape[0]] = rows_samples
+    samples[start_idx: start_idx + rows_samples.shape[0]] = rows_samples
 
 
 @task(samples_path=FILE_INOUT, row_blocks={Type: COLLECTION_IN, Depth: 2})
@@ -420,7 +420,7 @@ def _fill_features_file(samples_path, row_blocks, start_idx):
     rows_samples = Array._merge_blocks(row_blocks)
     rows_samples = rows_samples.astype(dtype="float32", casting="same_kind")
     samples = np.lib.format.open_memmap(samples_path, mode="r+")
-    samples[:, start_idx : start_idx + rows_samples.shape[0]] = rows_samples.T
+    samples[:, start_idx: start_idx + rows_samples.shape[0]] = rows_samples.T
 
 
 @task(targets_path=FILE_INOUT, row_blocks={Type: COLLECTION_IN, Depth: 2})
diff --git a/tests/test_rf_dataset.py b/tests/test_rf_dataset.py
index 86eceaf8..de55fc76 100644
--- a/tests/test_rf_dataset.py
+++ b/tests/test_rf_dataset.py
@@ -143,7 +143,7 @@ def _fill_samples_file(samples_path, row_blocks, start_idx, fortran_order):
     samples = np.lib.format.open_memmap(
         samples_path, mode="r+", fortran_order=fortran_order
     )
-    samples[start_idx : start_idx + rows_samples.shape[0]] = rows_samples
+    samples[start_idx: start_idx + rows_samples.shape[0]] = rows_samples
 
 
 def _fill_features_file(samples_path, row_blocks, start_idx, fortran_order):
@@ -152,7 +152,7 @@ def _fill_features_file(samples_path, row_blocks, start_idx, fortran_order):
     samples = np.lib.format.open_memmap(
         samples_path, mode="r+", fortran_order=fortran_order
     )
-    samples[:, start_idx : start_idx + rows_samples.shape[0]] = rows_samples.T
+    samples[:, start_idx: start_idx + rows_samples.shape[0]] = rows_samples.T
 
 
 def _fill_targets_file(targets_path, row_blocks):