diff --git a/README.md b/README.md
index 5d589f4d..5d8ace58 100644
--- a/README.md
+++ b/README.md
@@ -129,7 +129,7 @@ def result_to_df(result: ResultSet) -> pd.DataFrame:
         col_name = columns[col_num]
         col_list = result.column_values(col_name)
         d[col_name] = [x.cast() for x in col_list]
-    return pd.DataFrame.from_dict(d, columns=columns)
+    return pd.DataFrame.from_dict(d, orient='columns')
 
 # define a config
 config = Config()
diff --git a/example/FormatResp.py b/example/FormatResp.py
index 9e084609..52a16500 100644
--- a/example/FormatResp.py
+++ b/example/FormatResp.py
@@ -36,7 +36,6 @@ def result_to_df(result: ResultSet) -> pd.DataFrame:
 ################################
 cast_as = {
     Value.NVAL: "as_null",
-    Value.__EMPTY__: "as_empty",
     Value.BVAL: "as_bool",
     Value.IVAL: "as_int",
     Value.FVAL: "as_double",
@@ -55,12 +54,18 @@ def result_to_df(result: ResultSet) -> pd.DataFrame:
 }
 
 
-def customized_cast_with_dict(val: ValueWrapper):
+def cast(val: ValueWrapper):
     _type = val._value.getType()
-    method = cast_as.get(_type)
-    if method is not None:
-        return getattr(val, method, lambda *args, **kwargs: None)()
-    raise KeyError("No such key: {}".format(_type))
+    if _type == Value.__EMPTY__:
+        return None
+    if _type in cast_as:
+        return getattr(val, cast_as[_type])()
+    if _type == Value.LVAL:
+        return [x.cast() for x in val.as_list()]
+    if _type == Value.UVAL:
+        return {x.cast() for x in val.as_set()}
+    if _type == Value.MVAL:
+        return {k: v.cast() for k, v in val.as_map().items()}
 
 
 def print_resp(resp: ResultSet):
@@ -70,7 +75,7 @@ def print_resp(resp: ResultSet):
     for recode in resp:
         value_list = []
         for col in recode:
-            val = customized_cast_with_dict(col)
+            val = cast(col)
             value_list.append(val)
         output_table.add_row(value_list)
     print(output_table)
diff --git a/nebula3/data/DataObject.py b/nebula3/data/DataObject.py
index eb784ffe..a66b824c 100644
--- a/nebula3/data/DataObject.py
+++ b/nebula3/data/DataObject.py
@@ -26,7 +26,6 @@
 
 __AS_MAP__ = {
     Value.NVAL: "as_null",
-    Value.__EMPTY__: "as_empty",
     Value.BVAL: "as_bool",
     Value.IVAL: "as_int",
     Value.FVAL: "as_double",
@@ -686,6 +685,8 @@ def cast(self) -> Any:
         : return: Any type (e.g. int, float, List[Dict[str, int]], Set[List[float]])
         """
         _type = self._value.getType()
+        if _type == Value.__EMPTY__:
+            return None
         if _type in __AS_MAP__:
             # Considering the most efficient way, we should call `cast` in every iterable method over their items,
             # such as `as_list`, `as_set`, and `as_map`. However, the returned type will change and cause incompatibility.