add py_reader doc

python/paddle/fluid/layers/io.py

@@ -563,22 +563,26 @@ def _py_reader(capacity,
 
     def start_provide_thread(func):
         def __provider_thread__():
-            for tensors in func():
-                array = core.LoDTensorArray()
-                for item in tensors:
-                    if not isinstance(item, core.LoDTensor):
-                        tmp = core.LoDTensor()
-                        tmp.set(item, core.CPUPlace())
-                        item = tmp
-
-                    array.append(item)
-
-                if reader.exited:
-                    break
-                feed_queue.push(array)
-                if reader.exited:
-                    break
-            feed_queue.close()
+            try:
+                for tensors in func():
+                    array = core.LoDTensorArray()
+                    for item in tensors:
+                        if not isinstance(item, core.LoDTensor):
+                            tmp = core.LoDTensor()
+                            tmp.set(item, core.CPUPlace())
+                            item = tmp
+
+                        array.append(item)
+
+                    if reader.exited:
+                        break
+                    feed_queue.push(array)
+                    if reader.exited:
+                        break
+                feed_queue.close()
+            except Exception as ex:
+                feed_queue.close()
+                raise ex
 
         reader.thread = threading.Thread(target=__provider_thread__)
         reader.thread.daemon = True
@@ -692,6 +696,11 @@ def py_reader(capacity,
         >>>             exe.run(fetch_list=[loss.name])
         >>>     except fluid.core.EOFException:
         >>>         reader.reset()
+        >>>
+        >>> ...
+        >>>
+        >>> fluid.io.save_inference_model(dirname='./model', feeded_var_names=[img, label],
+        >>>     target_vars=[loss], executor=fluid.Executor(fluid.CUDAPlace(0)))  
 
         2. When training and testing are both performed, two different
         :code:`py_reader` should be created with different names, e.g.:

python/paddle/fluid/reader.py

@@ -250,20 +250,24 @@ class PyReader(object):
 
     def _start(self):
         def __thread_main__():
-            for tensors in self._tensor_reader():
-                array = core.LoDTensorArray()
-                for item in tensors:
-                    if not isinstance(item, core.LoDTensor):
-                        tmp = core.LoDTensor()
-                        tmp.set(item, core.CPUPlace())
-                        item = tmp
-
-                    array.append(item)
-
-                if not self._queue.push(array):
-                    break
-
-            self._queue.close()
+            try:
+                for tensors in self._tensor_reader():
+                    array = core.LoDTensorArray()
+                    for item in tensors:
+                        if not isinstance(item, core.LoDTensor):
+                            tmp = core.LoDTensor()
+                            tmp.set(item, core.CPUPlace())
+                            item = tmp
+
+                        array.append(item)
+
+                    if not self._queue.push(array):
+                        break
+
+                self._queue.close()
+            except Exception as ex:
+                self._queue.close()
+                raise ex
 
         self._thread = threading.Thread(target=__thread_main__)
         self._thread.daemon = True