diff --git a/models/rank/logistic_regression/data/get_slot_data.py b/models/rank/logistic_regression/data/get_slot_data.py
index f0b95a79c70d7c9da8b327884c17206e6b76f731..f9605d50b6600f1d2bd324b7ab6dd8cc84a6ab49 100644
--- a/models/rank/logistic_regression/data/get_slot_data.py
+++ b/models/rank/logistic_regression/data/get_slot_data.py
@@ -79,8 +79,7 @@ class Reader(dg.MultiSlotDataGenerator):
                 v = i[1]
                 for j in v:
                     s += " " + k + ":" + str(j)
-            print(s.strip())
-            yield None
+            print(s.strip())  # add print for data preprocessing
 
         return data_iter
 
diff --git a/models/rank/logistic_regression/readme.md b/models/rank/logistic_regression/readme.md
index 84237b60abe6a84bf525a1b44936be02ebc6eea4..226667c535f6318350119ba93113a02116c5c5ef 100644
--- a/models/rank/logistic_regression/readme.md
+++ b/models/rank/logistic_regression/readme.md
@@ -156,9 +156,7 @@ class Reader(dg.MultiSlotDataGenerator):
                 v = i[1]
                 for j in v:
                     s += " " + k + ":" + str(j)
-            print(s.strip())
-            yield None
-
+            print(s.strip()) # add print for data preprocessing
         return data_iter