support multi-field for inference

python/paddle/v2/inference.py

@@ -41,17 +41,20 @@ class Inference(object):
             yield [each_result[field] for each_result in result]
 
     def infer(self, field='value', **kwargs):
+        if not isinstance(field, list) and not isinstance(field, tuple):
+            field = [field]
+
+        retv_list = []
+        for each_field in field:
             retv = None
-        for result in self.iter_infer_field(field=field, **kwargs):
+            for result in self.iter_infer_field(field=each_field, **kwargs):
                 if retv is None:
                     retv = [[]] * len(result)
                 for i, item in enumerate(result):
                     retv[i].append(item)
             retv = [numpy.concatenate(out) for out in retv]
-        if len(retv) == 1:
-            return retv[0]
-        else:
-            return retv
+            retv_list.append(retv[0] if len(retv) == 1 else retv)
+        return retv_list[0] if len(retv_list) == 1 else retv_list
 
 
 def infer(output_layer, parameters, input, feeding=None, field='value'):