ensure shuffling only once

toolkit.py

@@ -794,6 +794,12 @@ class ClassificationProject(object):
 
     def shuffle_training_data(self):
 
+        if not self.data_loaded:
+            raise ValueError("Data not loaded! can't shuffle training data!")
+
+        if self.data_shuffled:
+            logger.warning("Data already shuffled, won't shuffle again")
+
         np.random.seed(self.shuffle_seed)
 
         # touch property to make sure it is created