Merge pull request #1425 from helinwang/map

add decorator: map_readers, change from google python style to pep 287

python/paddle/reader/decorator.py

@@ -12,7 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__all__ = ['buffered', 'compose', 'chain', 'shuffle', 'ComposeNotAligned']
+__all__ = [
+    'map_readers', 'buffered', 'compose', 'chain', 'shuffle',
+    'ComposeNotAligned'
+]
 
 from Queue import Queue
 from threading import Thread
@@ -20,20 +23,38 @@ import itertools
 import random
 
 
+def map_readers(func, *readers):
+    """
+    Creates a data reader that outputs return value of function using
+    output of each data readers as arguments.
+
+    :param func: function to use.
+    :param *readers: readers whose outputs will be used as arguments of func.
+    :returns: the created data reader.
+    """
+
+    def reader():
+        rs = []
+        for r in readers:
+            rs.append(r())
+        for e in itertools.imap(func, *rs):
+            yield e
+
+    return reader
+
+
 def shuffle(reader, buf_size):
-    """Creates a data reader whose data output is suffled.
+    """
+    Creates a data reader whose data output is suffled.
 
     Output from the iterator that created by original reader will be
     buffered into shuffle buffer, and then shuffled. The size of shuffle buffer
     is determined by argument buf_size.
 
-    Args:
-        reader: the original reader whose output will be
-            shuffled.
-        buf_size: shuffle buffer size.
+    :param reader: the original reader whose output will be shuffled.
+    :param buf_size: shuffle buffer size.
 
-    Returns:
-        the new reader whose output is shuffled.
+    :returns:the new reader whose output is shuffled.
     """
 
     def data_reader():
@@ -55,7 +76,8 @@ def shuffle(reader, buf_size):
 
 
 def chain(*readers):
-    """Creates a data reader whose output is the outputs of input data
+    """
+    Creates a data reader whose output is the outputs of input data
     readers chained together.
 
     If input readers output following data entries:
@@ -65,11 +87,8 @@ def chain(*readers):
     The chained reader will output:
     [0, 0, 0, 1, 1, 1, 2, 2, 2]
 
-    Args:
-        readers: input readers.
-
-    Returns:
-        the new data reader.
+    :param readers: input readers.
+    :returns: the new data reader.
     """
 
     def reader():
@@ -88,24 +107,22 @@ class ComposeNotAligned(ValueError):
 
 
 def compose(*readers, **kwargs):
-    """Creates a data reader whose output is the combination of input readers.
+    """
+    Creates a data reader whose output is the combination of input readers.
 
     If input readers output following data entries:
     (1, 2)    3    (4, 5)
     The composed reader will output:
     (1, 2, 3, 4, 5)
 
-    Args:
-        *readers: readers that will be composed together.
-        check_alignment: If True, will check if input readers are aligned
+    :*readers: readers that will be composed together.
+    :check_alignment: if True, will check if input readers are aligned
         correctly. If False, will not check alignment and trailing outputs
         will be discarded. Defaults to True.
 
-    Returns:
-        the new data reader.
+    :returns: the new data reader.
 
-    Raises:
-        ComposeNotAligned: outputs of readers are not aligned.
+    :raises ComposeNotAligned: outputs of readers are not aligned.
         Will not raise when check_alignment is set to False.
     """
     check_alignment = kwargs.pop('check_alignment', True)
@@ -136,18 +153,17 @@ def compose(*readers, **kwargs):
 
 
 def buffered(reader, size):
-    """Creates a buffered data reader.
+    """
+    Creates a buffered data reader.
 
     The buffered data reader will read and save data entries into a
     buffer. Reading from the buffered data reader will proceed as long
     as the buffer is not empty.
     
-    Args:
-        reader: the data reader to read from.
-        size: max buffer size.
+    :param reader: the data reader to read from.
+    :param size: max buffer size.
     
-    Returns:
-        The buffered data reader.
+    :returns: the buffered data reader.
     """
 
     class EndSignal():

python/paddle/reader/tests/decorator_test.py

@@ -26,6 +26,22 @@ def reader_creator_10(dur):
     return reader
 
 
+class TestMap(unittest.TestCase):
+    def test_map(self):
+        d = {"h": 0, "i": 1}
+
+        def tokenize(x):
+            return d[x]
+
+        def read():
+            yield "h"
+            yield "i"
+
+        r = paddle.reader.map_readers(tokenize, read)
+        for i, e in enumerate(r()):
+            self.assertEqual(e, i)
+
+
 class TestBuffered(unittest.TestCase):
     def test_read(self):
         for size in range(20):