Add usage comment of plot.py

Author: shippingwang

python/paddle/utils/plot.py

@@ -11,11 +11,7 @@
 # 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.
-''' Plot data 
-    plot data as a curve figure
-    feed data by using append function
-    draw the figure by using plot function	
-'''
+
 import os
 
 
@@ -34,6 +30,15 @@ def reset(self):
 
 
 class Ploter(object):
+    '''
+        Plot input data in a 2D graph
+        
+        Args:
+            title: assign the title of input data.
+            step: x_axis of the data.
+            value: y_axis of the data.
+    '''
+
     def __init__(self, *args):
         self.__args__ = args
         self.__plot_data__ = {}
@@ -54,10 +59,18 @@ def __plot_is_disabled__(self):
         return self.__disable_plot__ == "True"
 
     def append(self, title, step, value):
-        '''Feed data
-	:param title: the title of the figure
-	:param step: x_axis
-	:param value: y_axis
+        '''
+	    Feed data
+	    
+            Args:
+                title: assign the group data to this subtitle.
+                step: the x_axis of data.
+                value: the y_axis of data.
+            
+            Examples:
+                .. code-block:: python
+                plot_curve = Ploter("Curve 1","Curve 2")
+                plot_curve.append(title="Curve 1",step=1,value=1)
 	'''
         assert isinstance(title, basestring)
         assert self.__plot_data__.has_key(title)
@@ -66,8 +79,16 @@ def append(self, title, step, value):
         data.append(step, value)
 
     def plot(self, path=None):
-        '''Plot data
-	:param path: save figure path   
+        '''
+            Plot data in a 2D graph
+
+            Args:
+                path: store the figure to this file path. Defaul None. 
+              
+            Examples:
+                .. code-block:: python
+                plot_curve = Ploter()
+                plot_cure.plot()
 	'''
         if self.__plot_is_disabled__():
             return