Polish code

python/paddle/fluid/tests/book/high-level-api/image_classification/test_image_classification_vgg.py

@@ -107,8 +107,7 @@ def train(use_cuda, train_program, parallel, params_dirname):
         event_handler=event_handler,
         feed_order=['pixel', 'label'])
 
-    if six.PY3:
-        del trainer
+    return trainer
 
 
 def infer(use_cuda, inference_program, parallel, params_dirname=None):
@@ -132,12 +131,15 @@ def main(use_cuda, parallel):
     save_path = "image_classification_vgg.inference.model"
 
     os.environ['CPU_NUM'] = str(4)
-    train(
+    trainer = train(
         use_cuda=use_cuda,
         train_program=train_network,
         params_dirname=save_path,
         parallel=parallel)
 
+    if six.PY3:
+        del trainer
+
     # FIXME(zcd): in the inference stage, the number of
     # input data is one, it is not appropriate to use parallel.
     if parallel and use_cuda:

python/paddle/fluid/tests/book/high-level-api/recognize_digits/test_recognize_digits_mlp.py

@@ -90,8 +90,7 @@ def train(use_cuda, train_program, params_dirname, parallel):
         reader=train_reader,
         feed_order=['img', 'label'])
 
-    if six.PY3:
-        del trainer
+    return trainer
 
 
 def infer(use_cuda, inference_program, parallel, params_dirname=None):
@@ -117,12 +116,15 @@ def main(use_cuda, parallel):
 
     # call train() with is_local argument to run distributed train
     os.environ['CPU_NUM'] = str(4)
-    train(
+    trainer = train(
         use_cuda=use_cuda,
         train_program=train_program,
         params_dirname=params_dirname,
         parallel=parallel)
 
+    if six.PY3:
+        del trainer
+
     # FIXME(zcd): in the inference stage, the number of
     # input data is one, it is not appropriate to use parallel.
     if parallel and use_cuda: