diff --git a/python/paddle/v2/reader/decorator.py b/python/paddle/v2/reader/decorator.py
index 68ffbd6f3d459b219aef7eb52749671e86025711..e432003129d2b8dea60138d08f13ec5e9d29a7ad 100644
--- a/python/paddle/v2/reader/decorator.py
+++ b/python/paddle/v2/reader/decorator.py
@@ -251,18 +251,19 @@ def xmap_readers(mapper, reader, process_num, buffer_size, order=False):
     in_queue = Queue(buffer_size)
     out_queue = Queue(buffer_size)
     out_order = [0]
+
     # define a worker to read samples from reader to in_queue
     def read_worker(reader, in_queue):
         for i in reader():
             in_queue.put(i)
         in_queue.put(end)
-    
+
     # define a worker to read samples from reader to in_queue with order flag
     def order_read_worker(reader, in_queue):
         in_order = 0
         for i in reader():
-            in_queue.put((in_order,i))
-            in_order+=1
+            in_queue.put((in_order, i))
+            in_order += 1
         in_queue.put(end)
 
     # start a read worker in a thread
@@ -281,7 +282,7 @@ def xmap_readers(mapper, reader, process_num, buffer_size, order=False):
             sample = in_queue.get()
         in_queue.put(end)
         out_queue.put(end)
-    
+
     # define a worker to handle samples from in_queue by mapper
     # and put mapped samples into out_queue by order
     def order_handle_worker(in_queue, out_queue, mapper, out_order):
@@ -292,18 +293,18 @@ def xmap_readers(mapper, reader, process_num, buffer_size, order=False):
             while order != out_order[0]:
                 pass
             out_queue.put(r)
-            out_order[0] += 1  
+            out_order[0] += 1
             ins = in_queue.get()
         in_queue.put(end)
         out_queue.put(end)
 
     # start several handle_workers
     target = order_handle_worker if order else handle_worker
-    args = (in_queue, out_queue, mapper, out_order) if order else (in_queue, out_queue, mapper)
+    args = (in_queue, out_queue, mapper, out_order) if order else (
+        in_queue, out_queue, mapper)
     workers = []
     for i in xrange(process_num):
-        worker = Thread(
-            target=target, args=args)
+        worker = Thread(target=target, args=args)
         worker.daemon = True
         workers.append(worker)
     for w in workers:
diff --git a/python/paddle/v2/reader/tests/decorator_test.py b/python/paddle/v2/reader/tests/decorator_test.py
index 76db91a44b8d75f1af7271d5f4f94ea21c51d943..0bd773395507c074d962084cca8842a2026e798a 100644
--- a/python/paddle/v2/reader/tests/decorator_test.py
+++ b/python/paddle/v2/reader/tests/decorator_test.py
@@ -120,10 +120,12 @@ class TestShuffle(unittest.TestCase):
                 total += 1
             self.assertEqual(total, 10)
 
+
 class TestXmap(unittest.TestCase):
     def test_xmap(self):
         def mapper(x):
             return (x + 1)
+
         orders = (True, False)
         thread_nums = (1, 2, 4, 8, 16)
         buffered_size = (1, 2, 4, 8, 16)
@@ -131,13 +133,15 @@ class TestXmap(unittest.TestCase):
             for tNum in thread_nums:
                 for size in buffered_size:
                     result = []
-                    for i in paddle.v2.reader.xmap_readers(mapper, reader_creator_10(), tNum, size, order)():
+                    for i in paddle.v2.reader.xmap_readers(mapper,
+                                                           reader_creator_10(),
+                                                           tNum, size, order)():
                         result.append(i)
                     if not order:
                         result.sort()
                     for idx, e in enumerate(result):
                         self.assertEqual(e, mapper(idx))
-                    
+
 
 if __name__ == '__main__':
     unittest.main()