diff --git a/paddleslim/pantheon/student.py b/paddleslim/pantheon/student.py
index 54b75ab20afa3008b849966993b6f5b07f2af343..e4f6b3e16886eecdc1ece841da283b948b6b4e8b 100644
--- a/paddleslim/pantheon/student.py
+++ b/paddleslim/pantheon/student.py
@@ -222,7 +222,7 @@ class Student(object):
         self._started = True
 
     def _merge_knowledge(self, knowledge):
-        for k, tensors in knowledge.items():
+        for k, tensors in list(knowledge.items()):
             if len(tensors) == 0:
                 del knowledge[k]
             elif len(tensors) == 1:
@@ -308,7 +308,7 @@ class Student(object):
             print("Knowledge merging strategy: {}".format(
                 self._merge_strategy))
             print("Knowledge description after merging:")
-            for schema, desc in knowledge_desc.items():
+            for schema, desc in list(knowledge_desc.items()):
                 print("{}: {}".format(schema, desc))
 
             self._knowledge_desc = knowledge_desc
@@ -426,13 +426,13 @@ class Student(object):
             end_received = [0] * len(queues)
             while True:
                 knowledge = OrderedDict(
-                    [(k, []) for k, v in self._knowledge_desc.items()])
+                    [(k, []) for k, v in list(self._knowledge_desc.items())])
                 for idx, receiver in enumerate(data_receivers):
                     if not end_received[idx]:
                         batch_samples = receiver.next(
                         ) if six.PY2 else receiver.__next__()
                         if not isinstance(batch_samples, EndSignal):
-                            for k, v in batch_samples.items():
+                            for k, v in list(batch_samples.items()):
                                 knowledge[k].append(v)
                         else:
                             end_received[idx] = 1
diff --git a/paddleslim/pantheon/teacher.py b/paddleslim/pantheon/teacher.py
index 9a17f6c788790a82e1a865817144769dcb1cfb4f..425257e18886940cac98ef5a5a2df356f2e6ae67 100644
--- a/paddleslim/pantheon/teacher.py
+++ b/paddleslim/pantheon/teacher.py
@@ -231,7 +231,7 @@ class Teacher(object):
                 "The knowledge data should be a dict or OrderedDict!")
 
         knowledge_desc = {}
-        for name, value in knowledge.items():
+        for name, value in list(knowledge.items()):
             knowledge_desc[name] = {
                 "shape": [-1] + list(value.shape[1:]),
                 "dtype": str(value.dtype),
@@ -294,7 +294,8 @@ class Teacher(object):
             times (int): The maximum repeated serving times. Default 1. Whenever 
                          the public method 'get_knowledge_generator()' in Student 
                          object called once, the serving times will be added one, 
-                         until reaching the maximum and ending the service.
+                         until reaching the maximum and ending the service. Only 
+                         valid in online mode, and will be ignored in offline mode.
         """
         if not self._started:
             raise ValueError("The method start() should be called first!")
@@ -339,9 +340,12 @@ class Teacher(object):
         if not times > 0:
             raise ValueError("Repeated serving times should be positive!")
         self._times = times
+        if self._times > 1 and self._out_file:
+            self._times = 1
+            print("WARNING: args 'times' will be ignored in offline mode")
 
         desc = {}
-        for name, var in schema.items():
+        for name, var in list(schema.items()):
             if not isinstance(var, fluid.framework.Variable):
                 raise ValueError(
                     "The member of schema must be fluid Variable.")
@@ -412,10 +416,14 @@ class Teacher(object):
                 else:
                     if self._knowledge_queue:
                         self._knowledge_queue.put(EndSignal())
+                    # should close file in child thread to wait for all 
+                    # writing finished
+                    if self._out_file:
+                        self._out_file.close()
 
         # Asynchronous output
         out_buf_queue = Queue.Queue(self._buf_size)
-        schema_keys, schema_vars = zip(*self._schema.items())
+        schema_keys, schema_vars = zip(*list(self._schema.items()))
         out_thread = Thread(target=writer, args=(out_buf_queue, schema_keys))
         out_thread.daemon = True
         out_thread.start()
@@ -424,8 +432,9 @@ class Teacher(object):
             self._program).with_data_parallel()
 
         print("Knowledge description {}".format(self._knowledge_desc))
-        print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(time.time())) +
-              "  Teacher begins to serve ...")
+        print(
+            time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(time.time())) +
+            "  Teacher begins to serve ...")
         # For offline dump, write the knowledge description to the head of file
         if self._out_file:
             self._out_file.write(pickle.dumps(self._knowledge_desc))
@@ -491,11 +500,10 @@ class Teacher(object):
 
         if self._knowledge_queue:
             self._knowledge_queue.join()
-        print(time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(time.time())) +
-              "  Teacher ends serving.")
+        print(
+            time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(time.time())) +
+            "  Teacher ends serving.")
 
     def __del__(self):
         if self._manager:
             self._manager.shutdown()
-        if self._out_file:
-            self._out_file.close()