rename args and add comments

1. rename 'useXmap' to 'use_xmap'
2. add comments about exchanging train data and test data

python/paddle/v2/dataset/flowers.py

@@ -46,6 +46,12 @@ SETID_URL = 'http://www.robots.ox.ac.uk/~vgg/data/flowers/102/setid.mat'
 DATA_MD5 = '52808999861908f626f3c1f4e79d11fa'
 LABEL_MD5 = 'e0620be6f572b9609742df49c70aed4d'
 SETID_MD5 = 'a5357ecc9cb78c4bef273ce3793fc85c'
+# In official 'readme', tstid is the flag of test data
+# and trnid is the flag of train data. But test data is more than train data.
+# So we exchange the train data and test data.
+TRAIN_FLAG = 'tstid'
+TEST_FLAG = 'trnid'
+VALID_FLAG = 'valid'
 
 
 def default_mapper(sample):
@@ -64,7 +70,7 @@ def reader_creator(data_file,
                    dataset_name,
                    mapper=default_mapper,
                    buffered_size=1024,
-                   useXmap=True):
+                   use_xmap=True):
     '''
     1. read images from tar file and
         merge images into batch files in 102flowers.tgz_batch/
@@ -106,13 +112,13 @@ def reader_creator(data_file,
             for sample, label in itertools.izip(data, batch['label']):
                 yield sample, int(label)
 
-    if useXmap:
+    if use_xmap:
         return xmap_readers(mapper, reader, cpu_count(), buffered_size)
     else:
         return map_readers(mapper, reader)
 
 
-def train(mapper=default_mapper, buffered_size=1024, useXmap=True):
+def train(mapper=default_mapper, buffered_size=1024, use_xmap=True):
     '''
     Create flowers training set reader.
     It returns a reader, each sample in the reader is
@@ -131,11 +137,11 @@ def train(mapper=default_mapper, buffered_size=1024, useXmap=True):
     return reader_creator(
         download(DATA_URL, 'flowers', DATA_MD5),
         download(LABEL_URL, 'flowers', LABEL_MD5),
-        download(SETID_URL, 'flowers', SETID_MD5), 'tstid', mapper,
-        buffered_size, useXmap)
+        download(SETID_URL, 'flowers', SETID_MD5), TRAIN_FLAG, mapper,
+        buffered_size, use_xmap)
 
 
-def test(mapper=default_mapper, buffered_size=1024, useXmap=True):
+def test(mapper=default_mapper, buffered_size=1024, use_xmap=True):
     '''
     Create flowers test set reader.
     It returns a reader, each sample in the reader is
@@ -154,11 +160,11 @@ def test(mapper=default_mapper, buffered_size=1024, useXmap=True):
     return reader_creator(
         download(DATA_URL, 'flowers', DATA_MD5),
         download(LABEL_URL, 'flowers', LABEL_MD5),
-        download(SETID_URL, 'flowers', SETID_MD5), 'trnid', mapper,
-        buffered_size, useXmap)
+        download(SETID_URL, 'flowers', SETID_MD5), TEST_FLAG, mapper,
+        buffered_size, use_xmap)
 
 
-def valid(mapper=default_mapper, buffered_size=1024, useXmap=True):
+def valid(mapper=default_mapper, buffered_size=1024, use_xmap=True):
     '''
     Create flowers validation set reader.
     It returns a reader, each sample in the reader is
@@ -177,8 +183,8 @@ def valid(mapper=default_mapper, buffered_size=1024, useXmap=True):
     return reader_creator(
         download(DATA_URL, 'flowers', DATA_MD5),
         download(LABEL_URL, 'flowers', LABEL_MD5),
-        download(SETID_URL, 'flowers', SETID_MD5), 'valid', mapper,
-        buffered_size, useXmap)
+        download(SETID_URL, 'flowers', SETID_MD5), VALID_FLAG, mapper,
+        buffered_size, use_xmap)
 
 
 def fetch():