diff --git a/README.md b/README.md
index ea3cbb0..748db1e 100644
--- a/README.md
+++ b/README.md
@@ -66,6 +66,7 @@ python >= 3
 
 ````shell
 pip install canal-python
+pip install protobuf
 ````
 
 ### 建立与Canal的连接
@@ -125,5 +126,5 @@ while True:
 client.disconnect()
 ````
 
-更多详情请查看 [Sample](https://github.com/haozi3156666/canal-python/blob/master/example.py)
+更多详情请查看 [Sample](https://github.com/haozi3156666/canal-python/blob/master/canal/example.py)
 
diff --git a/canal/client.py b/canal/client.py
index 567b592..0455050 100644
--- a/canal/client.py
+++ b/canal/client.py
@@ -171,16 +171,13 @@ def rollback(self, batch_id):
                 format_data = dict()
                 if event_type == EntryProtocol_pb2.EventType.DELETE:
                     for column in row.beforeColumns:
-                        format_data = {
-                            column.name: column.value
-                        }
+                        format_data[column.name] = column.value
                 elif event_type == EntryProtocol_pb2.EventType.INSERT:
                     for column in row.afterColumns:
-                        format_data = {
-                            column.name: column.value
-                        }
+                        format_data[column.name] = column.value
                 else:
-                    format_data['before'] = format_data['after'] = dict()
+                    format_data['before'] = dict()
+                    format_data['after'] = dict()
                     for column in row.beforeColumns:
                         format_data['before'][column.name] = column.value
                     for column in row.afterColumns:
diff --git a/canal/example.py b/canal/example.py
index de68f90..361ce9d 100644
--- a/canal/example.py
+++ b/canal/example.py
@@ -29,16 +29,13 @@
             format_data = dict()
             if event_type == EntryProtocol_pb2.EventType.DELETE:
                 for column in row.beforeColumns:
-                    format_data = {
-                        column.name: column.value
-                    }
+                    format_data[column.name] = column.value
             elif event_type == EntryProtocol_pb2.EventType.INSERT:
                 for column in row.afterColumns:
-                    format_data = {
-                        column.name: column.value
-                    }
+                    format_data[column.name] = column.value
             else:
-                format_data['before'] = format_data['after'] = dict()
+                format_data['before'] = dict()
+                format_data['after'] = dict()
                 for column in row.beforeColumns:
                     format_data['before'][column.name] = column.value
                 for column in row.afterColumns: