diff --git a/doc/api/index_cn.rst b/doc/api/index_cn.rst
index 874dd9cb2278ce36a029b8745f2d82a7e642128e..fca981221e490686e468ae8d385d844d49767883 100644
--- a/doc/api/index_cn.rst
+++ b/doc/api/index_cn.rst
@@ -1,2 +1,26 @@
 API
-===
\ No newline at end of file
+===
+
+模型配置 API
+------------
+
+..  toctree::
+    :maxdepth: 1
+
+    v2/model_configs.rst
+
+数据 API
+--------
+
+..  toctree::
+    :maxdepth: 1
+
+    v2/data.rst
+
+训练 API
+--------
+
+..	toctree::
+	:maxdepth: 1
+
+	v2/run_logic.rst
\ No newline at end of file
diff --git a/doc/api/index_en.rst b/doc/api/index_en.rst
index deeeed26fa6ee24451dff6dad619438440ed60e8..f0ad0fb2aee7345db1dd5f175a342598366f5e3c 100644
--- a/doc/api/index_en.rst
+++ b/doc/api/index_en.rst
@@ -16,3 +16,11 @@ Data API
     :maxdepth: 1
 
     v2/data.rst
+
+Train API
+---------
+
+..	toctree::
+	:maxdepth: 1
+
+	v2/run_logic.rst
\ No newline at end of file
diff --git a/doc/api/v2/data.rst b/doc/api/v2/data.rst
index 65e57f2344bd5ee6a68b491d2eb8317a61852422..49f70b3671bdff1d204617b3138dc45099ba6a33 100644
--- a/doc/api/v2/data.rst
+++ b/doc/api/v2/data.rst
@@ -2,5 +2,80 @@
 DataTypes
 #########
 
-..	automodule:: paddle.v2.data_type
-	:members:
+..  automodule:: paddle.v2.data_type
+    :members:
+
+##########
+DataFeeder
+##########
+
+..  automodule:: paddle.v2.data_feeder
+    :members:
+
+######
+Reader
+######
+
+..  automodule:: paddle.v2.reader
+    :members:
+
+..  automodule:: paddle.v2.reader.creator
+    :members:
+
+#######
+Dataset
+#######
+
+..  automodule:: paddle.v2.dataset
+    :members:
+
+
+mnist
++++++
+
+..  automodule:: paddle.v2.dataset.mnist
+    :members:
+
+
+cifar
++++++
+
+..  automodule:: paddle.v2.dataset.cifar
+    :members:
+
+conll05
++++++++
+
+..  automodule:: paddle.v2.dataset.conll05
+    :members:
+
+imdb
+++++
+
+..  automodule:: paddle.v2.dataset.imdb
+    :members:
+
+imikolov
+++++++++
+
+..  automodule:: paddle.v2.dataset.imikolov
+    :members:
+
+movielens
++++++++++
+
+..  automodule:: paddle.v2.dataset.movielens
+    :members:
+
+sentiment
++++++++++
+
+..  automodule:: paddle.v2.dataset.sentiment
+    :members:
+
+uci_housing
++++++++++++
+
+..  automodule:: paddle.v2.dataset.uci_housing
+    :members:
+
diff --git a/doc/api/v2/model_configs.rst b/doc/api/v2/model_configs.rst
index b848bd7045a701a1a0d6e6b53da971ada2c569f5..52e2dcd53055c68f2418adc0ac8a6a36b10dc22c 100644
--- a/doc/api/v2/model_configs.rst
+++ b/doc/api/v2/model_configs.rst
@@ -33,3 +33,10 @@ Networks
 
 ..	automodule:: paddle.v2.networks
 	:members:
+
+==========
+Optimizers
+==========
+
+..	automodule:: paddle.v2.optimizers
+	:members:
diff --git a/doc/api/v2/run_logic.rst b/doc/api/v2/run_logic.rst
new file mode 100644
index 0000000000000000000000000000000000000000..522093f8aeedb81c20e0aefa324e0567851af889
--- /dev/null
+++ b/doc/api/v2/run_logic.rst
@@ -0,0 +1,22 @@
+==========
+Parameters
+==========
+
+..  automodule:: paddle.v2.parameters
+    :members:
+
+
+=======
+Trainer
+=======
+
+..	automodule:: paddle.v2.trainer
+	:members:
+
+
+=====
+Event
+=====
+
+..	automodule:: paddle.v2.event
+	:members:
diff --git a/doc/design/reader/README.md b/doc/design/reader/README.md
index 03119fdd74502a4534c2e6a576580ce96a721c7e..f21f7af520df5171798326818ecb97c3bcd14a12 100644
--- a/doc/design/reader/README.md
+++ b/doc/design/reader/README.md
@@ -23,19 +23,19 @@ An example implementation for single item data reader creator:
 
 ```python
 def reader_creator_random_image(width, height):
-	def reader():
-		while True:
-			yield numpy.random.uniform(-1, 1, size=width*height)
-	return reader
+    def reader():
+        while True:
+            yield numpy.random.uniform(-1, 1, size=width*height)
+    return reader
 ```
 
 An example implementation for multiple item data reader creator:
 ```python
-def reader_creator_random_imageand_label(widht, height, label):
-	def reader():
-		while True:
-			yield numpy.random.uniform(-1, 1, size=width*height), label
-	return reader
+def reader_creator_random_image_and_label(width, height, label):
+    def reader():
+        while True:
+            yield numpy.random.uniform(-1, 1, size=width*height), label
+    return reader
 ```
 
 ## Batch Reader Interface
@@ -74,11 +74,11 @@ mnist_train_batch_reader = paddle.batch(mnist_train, 128)
 Also easy to create custom batch reader:
 ```python
 def custom_batch_reader():
-	while True:
-		batch = []
-		for i in xrange(128):
-			batch.append((numpy.random.uniform(-1, 1, 28*28),)) # note that it's a tuple being appended.
-		yield batch
+    while True:
+        batch = []
+        for i in xrange(128):
+            batch.append((numpy.random.uniform(-1, 1, 28*28),)) # note that it's a tuple being appended.
+        yield batch
 
 mnist_random_image_batch_reader = custom_batch_reader
 ```
@@ -123,16 +123,16 @@ We can do:
 
 ```python
 def reader_creator_random_image(width, height):
-	def reader():
-		while True:
-			yield numpy.random.uniform(-1, 1, size=width*height)
-	return reader
+    def reader():
+        while True:
+            yield numpy.random.uniform(-1, 1, size=width*height)
+    return reader
 
 def reader_creator_bool(t):
-	def reader:
-		while True:
-			yield t
-	return reader
+    def reader:
+        while True:
+            yield t
+    return reader
 
 true_reader = reader_creator_bool(True)
 false_reader = reader_creator_bool(False)
@@ -172,18 +172,18 @@ We decided to use dictionary (`{"image":0, "label":1}`) instead of list (`["imag
 
 ```python
 def image_reader_creator(image_path, label_path, n):
-	def reader():
-		f = open(image_path)
-		l = open(label_path)
-		images = numpy.fromfile(
-			f, 'ubyte', count=n * 28 * 28).reshape((n, 28 * 28)).astype('float32')
-		images = images / 255.0 * 2.0 - 1.0
-		labels = numpy.fromfile(l, 'ubyte', count=n).astype("int")
-		for i in xrange(n):
-			yield images[i, :], labels[i] # a single entry of data is created each time
-		f.close()
-		l.close()
-	return reader
+    def reader():
+        f = open(image_path)
+        l = open(label_path)
+        images = numpy.fromfile(
+            f, 'ubyte', count=n * 28 * 28).reshape((n, 28 * 28)).astype('float32')
+        images = images / 255.0 * 2.0 - 1.0
+        labels = numpy.fromfile(l, 'ubyte', count=n).astype("int")
+        for i in xrange(n):
+            yield images[i, :], labels[i] # a single entry of data is created each time
+        f.close()
+        l.close()
+    return reader
 
 # images_reader_creator creates a reader
 reader = image_reader_creator("/path/to/image_file", "/path/to/label_file", 1024)
@@ -196,7 +196,7 @@ An example implementation of paddle.train could be:
 
 ```python
 def train(batch_reader, mapping, batch_size, total_pass):
-	for pass_idx in range(total_pass):
-		for mini_batch in batch_reader(): # this loop will never end in online learning.
-			do_forward_backward(mini_batch, mapping)
+    for pass_idx in range(total_pass):
+        for mini_batch in batch_reader(): # this loop will never end in online learning.
+            do_forward_backward(mini_batch, mapping)
 ```
diff --git a/python/paddle/v2/data_feeder.py b/python/paddle/v2/data_feeder.py
index 3b106e100cff7539611d95bb4123b4e0dfbfa6cb..b7465238be8138e47913b7bd3f1c669ed9653958 100644
--- a/python/paddle/v2/data_feeder.py
+++ b/python/paddle/v2/data_feeder.py
@@ -12,8 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from py_paddle import swig_paddle
 from py_paddle import DataProviderConverter
+
 import data_type
 
 __all__ = ['DataFeeder']
@@ -29,7 +29,10 @@ class DataFeeder(DataProviderConverter):
     to feed it to C++ interface.
     
     The example usage:
-    
+
+
+    ..  code-block:: python
+
         data_types = [('image', paddle.data_type.dense_vector(784)),
                       ('label', paddle.data_type.integer_value(10))]
         reader_dict = {'image':0, 'label':1}
@@ -43,20 +46,24 @@ class DataFeeder(DataProviderConverter):
         #                       [ [1.0,2.0,3.0,4.0], 5, [6,7,8] ]   # second sample
         #                     ]
         arg = feeder(minibatch_data)
+
+    ..  note::
+
+        This module is for internal use only. Users should use the `reader`
+        interface.
+
+
+
+    :param data_types: A list to specify data name and type. Each item is
+                       a tuple of (data_name, data_type).
+
+    :type data_types: list
+    :param reader_dict: A dictionary to specify the position of each data
+                        in the input data.
+    :type reader_dict: dict
     """
 
     def __init__(self, data_types, reader_dict):
-        """
-        :param data_types: A list to specify data name and type. Each item is
-                           a tuple of (data_name, data_type). For example:
-                           [('image', paddle.data_type.dense_vector(784)),
-                            ('label', paddle.data_type.integer_value(10))]
-
-        :type data_types: A list of tuple
-        :param reader_dict: A dictionary to specify the position of each data
-                            in the input data.
-        :type reader_dict: dict()
-        """
         self.input_names = []
         input_types = []
         self.reader_dict = reader_dict
@@ -70,22 +77,12 @@ class DataFeeder(DataProviderConverter):
         """
         :param dat: A list of mini-batch data. Each sample is a list or tuple
                     one feature or multiple features.
-                    for example:
-                    [ 
-                      ([0.2, 0.2], ), # first sample
-                      ([0.8, 0.3], ), # second sample
-                    ]
-                    or,
-                    [ 
-                      [[0.2, 0.2], ], # first sample
-                      [[0.8, 0.3], ], # second sample
-                    ]
-
-        :type dat: List
+
+        :type dat: list
         :param argument: An Arguments object contains this mini-batch data with
                          one or multiple features. The Arguments definition is
                          in the API.
-        :type argument: swig_paddle.Arguments
+        :type argument: py_paddle.swig_paddle.Arguments
         """
 
         def reorder_data(data):
diff --git a/python/paddle/v2/dataset/__init__.py b/python/paddle/v2/dataset/__init__.py
index 82f11a7c41149c2231130dc7c2205debb643aa89..9ef0277609d29ac45a47d56f3f3a7d621d73e043 100644
--- a/python/paddle/v2/dataset/__init__.py
+++ b/python/paddle/v2/dataset/__init__.py
@@ -11,6 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+"""
+Dataset package.
+"""
 
 import mnist
 import imikolov
diff --git a/python/paddle/v2/dataset/cifar.py b/python/paddle/v2/dataset/cifar.py
index 5c6f5d85567fa19f2835ee4f3951531b6dfd3209..d9f7a830ee60a331b55a1e218923e690103e1c5b 100644
--- a/python/paddle/v2/dataset/cifar.py
+++ b/python/paddle/v2/dataset/cifar.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 """
 CIFAR dataset: https://www.cs.toronto.edu/~kriz/cifar.html
+
+TODO(yuyang18): Complete the comments.
 """
 
 import cPickle
diff --git a/python/paddle/v2/dataset/conll05.py b/python/paddle/v2/dataset/conll05.py
index e96a701c1a944e2d6d84f897157cb357c5aa0824..9eab49ee39325c1c60fc511e0bd834e83aa987f0 100644
--- a/python/paddle/v2/dataset/conll05.py
+++ b/python/paddle/v2/dataset/conll05.py
@@ -16,15 +16,17 @@ import tarfile
 import gzip
 import itertools
 from common import download
-
-__all__ = ['test, get_dict', 'get_embedding']
 """
 Conll 2005 dataset.  Paddle semantic role labeling Book and demo use this
 dataset as an example. Because Conll 2005 is not free in public, the default
 downloaded URL is test set of Conll 2005 (which is public). Users can change
 URL and MD5 to their Conll dataset.
+
+TODO(yuyang18): Complete comments.
 """
 
+__all__ = ['test, get_dict', 'get_embedding']
+
 DATA_URL = 'http://www.cs.upc.edu/~srlconll/conll05st-tests.tar.gz'
 DATA_MD5 = '387719152ae52d60422c016e92a742fc'
 WORDDICT_URL = 'http://paddlepaddle.bj.bcebos.com/demo/srl_dict_and_embedding/wordDict.txt'
diff --git a/python/paddle/v2/dataset/imdb.py b/python/paddle/v2/dataset/imdb.py
index f27756a38a9cd809fdaaf92e7f8a72b681915fc8..76019d9f54020ff6f02c17eb6047cbd014a8ccf2 100644
--- a/python/paddle/v2/dataset/imdb.py
+++ b/python/paddle/v2/dataset/imdb.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 """
 IMDB dataset: http://ai.stanford.edu/%7Eamaas/data/sentiment/aclImdb_v1.tar.gz
+
+TODO(yuyang18): Complete comments.
 """
 
 import paddle.v2.dataset.common
diff --git a/python/paddle/v2/dataset/imikolov.py b/python/paddle/v2/dataset/imikolov.py
index deb556942d9b0490ffab8cef90aae8f365652129..97c160f111d09d61eb860c7f02552e635f2400a7 100644
--- a/python/paddle/v2/dataset/imikolov.py
+++ b/python/paddle/v2/dataset/imikolov.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 """
 imikolov's simple dataset: http://www.fit.vutbr.cz/~imikolov/rnnlm/
+
+Complete comments.
 """
 import paddle.v2.dataset.common
 import tarfile
diff --git a/python/paddle/v2/dataset/mnist.py b/python/paddle/v2/dataset/mnist.py
index 6a621a2aaad14bf9598b838ce7c2ebf297bb0d30..16f2fcb99de4cb1971a7375a97b5daa209ee95ef 100644
--- a/python/paddle/v2/dataset/mnist.py
+++ b/python/paddle/v2/dataset/mnist.py
@@ -13,6 +13,9 @@
 # limitations under the License.
 """
 MNIST dataset.
+
+This module will download dataset from http://yann.lecun.com/exdb/mnist/ and
+parse train set and test set into paddle reader creators.
 """
 import paddle.v2.dataset.common
 import subprocess
@@ -72,6 +75,15 @@ def reader_creator(image_filename, label_filename, buffer_size):
 
 
 def train():
+    """
+    MNIST train set creator.
+
+    It returns a reader creator, each sample in the reader is image pixels in
+    [0, 1] and label in [0, 9].
+
+    :return: Train reader creator
+    :rtype: callable
+    """
     return reader_creator(
         paddle.v2.dataset.common.download(TRAIN_IMAGE_URL, 'mnist',
                                           TRAIN_IMAGE_MD5),
@@ -80,6 +92,15 @@ def train():
 
 
 def test():
+    """
+    MNIST test set cretor.
+
+    It returns a reader creator, each sample in the reader is image pixels in
+    [0, 1] and label in [0, 9].
+
+    :return: Test reader creator.
+    :rtype: callable
+    """
     return reader_creator(
         paddle.v2.dataset.common.download(TEST_IMAGE_URL, 'mnist',
                                           TEST_IMAGE_MD5),
diff --git a/python/paddle/v2/dataset/movielens.py b/python/paddle/v2/dataset/movielens.py
index c22bcfa38b5f501732768dd4f62d8e088d57a7ff..dc65e8f8b6f04b078a3449c622478095086cecbe 100644
--- a/python/paddle/v2/dataset/movielens.py
+++ b/python/paddle/v2/dataset/movielens.py
@@ -11,6 +11,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+"""
+Movielens 1-M dataset.
+
+TODO(yuyang18): Complete comments.
+"""
 
 import zipfile
 from common import download
diff --git a/python/paddle/v2/dataset/sentiment.py b/python/paddle/v2/dataset/sentiment.py
index cbd08fa73684be42e8d8d2eb7b684d66894d7761..71689fd61b6b14a7b5072caff4e2fd48a7f74072 100644
--- a/python/paddle/v2/dataset/sentiment.py
+++ b/python/paddle/v2/dataset/sentiment.py
@@ -15,18 +15,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """
-The script fetch and preprocess movie_reviews data set
+The script fetch and preprocess movie_reviews data set that provided by NLTK
 
-that provided by NLTK
+TODO(yuyang18): Complete dataset.
 """
 
-import common
 import collections
-import nltk
-import numpy as np
 from itertools import chain
+
+import nltk
 from nltk.corpus import movie_reviews
 
+import common
+
 __all__ = ['train', 'test', 'get_word_dict']
 NUM_TRAINING_INSTANCES = 1600
 NUM_TOTAL_INSTANCES = 2000
diff --git a/python/paddle/v2/dataset/uci_housing.py b/python/paddle/v2/dataset/uci_housing.py
index b5a0537af66a3fae4e1b267ae25441a6cb75416b..27f454b137e3a40febd19cf085e2f4034cc16b24 100644
--- a/python/paddle/v2/dataset/uci_housing.py
+++ b/python/paddle/v2/dataset/uci_housing.py
@@ -11,6 +11,11 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+"""
+UCI Housing dataset.
+
+TODO(yuyang18): Complete comments.
+"""
 
 import numpy as np
 import os
diff --git a/python/paddle/v2/event.py b/python/paddle/v2/event.py
index a429e36b63c9e812332673b66f4d8b99f3303cf8..1ad52b8baa411269d29732685871a875df5185cc 100644
--- a/python/paddle/v2/event.py
+++ b/python/paddle/v2/event.py
@@ -34,6 +34,10 @@ class WithMetric(object):
 
 
 class TestResult(WithMetric):
+    """
+    Result that trainer.test return.
+    """
+
     def __init__(self, evaluator, cost):
         super(TestResult, self).__init__(evaluator)
         self.cost = cost
diff --git a/python/paddle/v2/optimizer.py b/python/paddle/v2/optimizer.py
index 10e255dc945efb8b20f09dc1806d2ba7ef856c55..1a01d95c205c0626374e1814a170ce2d58f23a60 100644
--- a/python/paddle/v2/optimizer.py
+++ b/python/paddle/v2/optimizer.py
@@ -1,7 +1,12 @@
 import py_paddle.swig_paddle as swig_api
-import paddle.trainer_config_helpers.optimizers as v1_optimizers
+
 import paddle.trainer_config_helpers.config_parser_utils as config_parser_utils
-import paddle.v2
+import paddle.trainer_config_helpers.optimizers as v1_optimizers
+"""
+Optimizers(update equation) for SGD method.
+
+TODO(yuyang18): Complete comments.
+"""
 
 __all__ = [
     'Momentum', 'Adam', 'Adamax', 'AdaGrad', 'DecayedAdaGrad', 'AdaDelta',
@@ -44,7 +49,7 @@ class Optimizer(object):
 class Momentum(Optimizer):
     def __init__(self, momentum=None, sparse=False, **kwargs):
         learning_method = v1_optimizers.MomentumOptimizer(
-            momentum=None, sparse=False)
+            momentum=momentum, sparse=sparse)
         super(Momentum, self).__init__(
             learning_method=learning_method, **kwargs)
 
diff --git a/python/paddle/v2/parameters.py b/python/paddle/v2/parameters.py
index 2a6026bcab1c8a373d8dd5eac480dec62a8eb3b9..7ee388f067c1868e4d940770342a0519aebbfa5e 100644
--- a/python/paddle/v2/parameters.py
+++ b/python/paddle/v2/parameters.py
@@ -10,6 +10,7 @@ __all__ = ['Parameters', 'create']
 def create(layers):
     """
     Create parameter pool by topology.
+
     :param layers:
     :return:
     """
@@ -67,6 +68,7 @@ class Parameters(object):
     def keys(self):
         """
         keys are the names of each parameter.
+
         :return: list of parameter name
         :rtype: list
         """
@@ -75,6 +77,7 @@ class Parameters(object):
     def names(self):
         """
         names of each parameter.
+
         :return: list of parameter name
         :rtype: list
         """
@@ -83,6 +86,7 @@ class Parameters(object):
     def has_key(self, key):
         """
         has_key return true if there are such parameter name == key
+
         :param key: Parameter name
         :type key: basestring
         :return: True if contains such key
@@ -136,6 +140,7 @@ class Parameters(object):
     def get_shape(self, key):
         """
         get shape of the parameter.
+
         :param key: parameter name
         :type key: basestring
         :return: parameter's shape
@@ -190,6 +195,7 @@ class Parameters(object):
     def set(self, parameter_name, value):
         """
         Set parameter by parameter name & matrix.
+
         :param parameter_name: parameter name
         :type parameter_name: basestring
         :param value: parameter matrix
diff --git a/python/paddle/v2/reader/__init__.py b/python/paddle/v2/reader/__init__.py
index 7373dc461b1d3115c03b37c5102a469a52aa7441..3b059735a924d58714cd88a761eb83143f1192d6 100644
--- a/python/paddle/v2/reader/__init__.py
+++ b/python/paddle/v2/reader/__init__.py
@@ -11,15 +11,64 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+"""
+At training and testing time, PaddlePaddle programs need to read data. To ease
+the users' work to write data reading code, we define that
 
-# It would be too lengthy to require our users to prefix decorators with `decorator`.
-# For example, we want the following line
-#
-#     r = paddle.reader.decorator.bufferd(paddle.reader.creator.text("hello.txt"))
-#
-# to be a shorter version:
-#
-#     r = paddle.reader.buffered(paddle.reader.creator.text("hello.txt"))
+- A *reader* is a function that reads data (from file, network, random number
+  generator, etc) and yields data items.
+- A *reader creator* is a function that returns a reader function.
+- A *reader decorator* is a function, which accepts one or more readers, and
+  returns a reader.
+- A *batch reader* is a function that reads data (from *reader*, file, network,
+  random number generator, etc) and yields a batch of data items.
+
+#####################
+Data Reader Interface
+#####################
+
+Indeed, *data reader* doesn't have to be a function that reads and yields data
+items. It can be any function with no parameter that creates a iterable
+(anything can be used in :code:`for x in iterable`)\:
+
+..  code-block:: python
+
+    iterable = data_reader()
+
+Element produced from the iterable should be a **single** entry of data,
+**not** a mini batch. That entry of data could be a single item, or a tuple of
+items.
+Item should be of `supported type <http://www.paddlepaddle.org/doc/ui/data_provider
+/pydataprovider2.html?highlight=dense_vector#input-types>`_ (e.g., numpy 1d
+array of float32, int, list of int)
+
+An example implementation for single item data reader creator:
+
+..  code-block:: python
+
+    def reader_creator_random_image(width, height):
+        def reader():
+            while True:
+                yield numpy.random.uniform(-1, 1, size=width*height)
+    return reader
+
+An example implementation for multiple item data reader creator:
+
+..  code-block:: python
+
+    def reader_creator_random_image_and_label(width, height, label):
+        def reader():
+            while True:
+                yield numpy.random.uniform(-1, 1, size=width*height), label
+    return reader
+
+
+TODO(yuyang18): Should we add whole design doc here?
+"""
+
+import decorator
 from decorator import *
 
 import creator
+
+__all__ = decorator.__all__ + ['creator']
diff --git a/python/paddle/v2/reader/creator.py b/python/paddle/v2/reader/creator.py
index 5a91bb0b8ef6d1874737386897f6c555eaec18d4..07142056f872db5113acdd296b17c52b343c1be6 100644
--- a/python/paddle/v2/reader/creator.py
+++ b/python/paddle/v2/reader/creator.py
@@ -11,6 +11,10 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+"""
+Creator package contains some simple reader creator, which could be used in user
+program.
+"""
 
 __all__ = ['np_array', 'text_file']
 
@@ -38,7 +42,7 @@ def np_array(x):
 def text_file(path):
     """
     Creates a data reader that outputs text line by line from given text file.
-    Trailing new line ('\n') of each line will be removed.
+    Trailing new line ('\\\\n') of each line will be removed.
 
     :path: path of the text file.
     :returns: data reader of text file
diff --git a/python/paddle/v2/reader/decorator.py b/python/paddle/v2/reader/decorator.py
index b7657e27764f099334ba3030c493a7607f323abe..401249972472311a41d7aef4c852014123e0def3 100644
--- a/python/paddle/v2/reader/decorator.py
+++ b/python/paddle/v2/reader/decorator.py
@@ -12,25 +12,27 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__all__ = [
-    'map_readers', 'buffered', 'compose', 'chain', 'shuffle',
-    'ComposeNotAligned', 'batched', 'firstn'
-]
-
 import itertools
 import random
 from Queue import Queue
 from threading import Thread
 
+__all__ = [
+    'map_readers', 'buffered', 'compose', 'chain', 'shuffle',
+    'ComposeNotAligned', 'batched', 'firstn'
+]
+
 
 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.
+    :param func: function to use. The type of func should be (Sample) => Sample
+    :type: callable
+    :param readers: readers whose outputs will be used as arguments of func.
+    :return: the created data reader.
+    :rtype: callable
     """
 
     def reader():
@@ -45,16 +47,19 @@ def map_readers(func, *readers):
 
 def shuffle(reader, buf_size):
     """
-    Creates a data reader whose data output is suffled.
+    Creates a data reader whose data output is shuffled.
 
     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.
 
     :param reader: the original reader whose output will be shuffled.
+    :type reader: callable
     :param buf_size: shuffle buffer size.
+    :type buf_size: int
 
-    :returns:the new reader whose output is shuffled.
+    :return: the new reader whose output is shuffled.
+    :rtype: callable
     """
 
     def data_reader():
@@ -88,7 +93,8 @@ def chain(*readers):
     [0, 0, 0, 1, 1, 1, 2, 2, 2]
 
     :param readers: input readers.
-    :returns: the new data reader.
+    :return: the new data reader.
+    :rtype: callable
     """
 
     def reader():
@@ -115,12 +121,13 @@ def compose(*readers, **kwargs):
     The composed reader will output:
     (1, 2, 3, 4, 5)
 
-    :*readers: readers that will be composed together.
-    :check_alignment: if True, will check if input readers are aligned
+    :param readers: readers that will be composed together.
+    :param 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.
+    :type check_alignment: bool
 
-    :returns: the new data reader.
+    :return: the new data reader.
 
     :raises ComposeNotAligned: outputs of readers are not aligned.
         Will not raise when check_alignment is set to False.
@@ -161,7 +168,9 @@ def buffered(reader, size):
     as the buffer is not empty.
     
     :param reader: the data reader to read from.
+    :type reader: callable
     :param size: max buffer size.
+    :type size: int
     
     :returns: the buffered data reader.
     """
@@ -196,9 +205,13 @@ def buffered(reader, size):
 def batched(reader, batch_size):
     """
     Create a batched reader.
+
     :param reader: the data reader to read from.
-    :param batch_size: batch_size
+    :type reader: callable
+    :param batch_size: size of each mini-batch
+    :type batch_size: int
     :return: the batched reader.
+    :rtype: callable
     """
 
     def batched_reader():
@@ -218,6 +231,13 @@ def batched(reader, batch_size):
 def firstn(reader, n):
     """
     Limit the max number of samples that reader could return.
+
+    :param reader: the data reader to read from.
+    :type reader: callable
+    :param n: the max number of samples that return.
+    :type n: int
+    :return: the decorated reader.
+    :rtype: callable
     """
 
     # TODO(yuyang18): Check if just drop the reader, could clean the opened
diff --git a/python/paddle/v2/trainer.py b/python/paddle/v2/trainer.py
index 8bcdd122b30bde91f652f351dddc27734fdf33cf..7b706721367085301a260756cc7f464356d6af3d 100644
--- a/python/paddle/v2/trainer.py
+++ b/python/paddle/v2/trainer.py
@@ -9,6 +9,10 @@ from . import optimizer as v2_optimizer
 from . import parameters as v2_parameters
 
 __all__ = ['SGD']
+"""
+Trainer package
+TODO(yuyang18): Complete comments.
+"""
 
 
 def default_event_handler(event):
@@ -22,14 +26,20 @@ def default_event_handler(event):
     pass
 
 
-class SGD():
-    def __init__(self, cost, parameters, update_equation):
-        """
-        Simple SGD Trainer.
+class SGD(object):
+    """
+    Simple SGD Trainer.
+    TODO(yuyang18): Complete comments
+
+    :param update_equation: The optimizer object.
+    :type update_equation: paddle.v2.optimizer.Optimizer
+    :param cost: Target cost that neural network should be optimized.
+    :type cost: paddle.v2.config_base.Layer
+    :param parameters: The parameters dictionary.
+    :type parameters: paddle.v2.parameters.Parameters
+    """
 
-        :param update_equation: The optimizer object.
-        :type update_equation: v2_optimizer.Optimizer
-        """
+    def __init__(self, cost, parameters, update_equation):
 
         if not isinstance(parameters, v2_parameters.Parameters):
             raise TypeError('parameters should be parameters')
@@ -56,8 +66,6 @@ class SGD():
         Training method. Will train num_passes of input data.
 
         :param reader:
-        :param topology: Network Topology, use one or more Layers to represent it.
-        :param parameters: The parameter pools.
         :param num_passes: The total train passes.
         :param event_handler: Event handler. A method will be invoked when event
                               occurred.