Mapkeys (#2900)

* added a map dict

* added a map dict

pytorch_lightning/core/step_result.py

@@ -347,6 +347,23 @@ class Result(Dict):
         if 'hiddens' in self:
             del self['hiddens']
 
+    def rename_keys(self, map_dict: dict):
+        """
+        Maps key values to the target values. Useful when renaming variables in mass.
+
+        Args:
+            map_dict:
+        """
+        meta = self.meta
+        for source, dest in map_dict.items():
+            # map the main keys
+            self[dest] = self[source]
+            del self[source]
+
+            # map meta
+            meta[dest] = meta[source]
+            del meta[source]
+
 
 def recursive_gather(outputs: Sequence[dict], result: Optional[MutableMapping] = None) -> Optional[MutableMapping]:
     for out in outputs:

tests/trainer/test_trainer_steps_result_return.py

@@ -532,3 +532,14 @@ def test_full_train_loop_with_results_obj_dp(tmpdir):
     assert 'train_step_metric' in seen_keys
     assert 'train_step_end_metric' in seen_keys
     assert 'epoch_train_epoch_end_metric' in seen_keys
+
+
+def test_result_map(tmpdir):
+    result = TrainResult()
+    result.log_dict({'x1': torch.tensor(1), 'x2': torch.tensor(2)})
+    result.rename_keys({'x1': 'y1', 'x2': 'y2'})
+
+    assert 'x1' not in result
+    assert 'x2' not in result
+    assert 'y1' in result
+    assert 'y2' in result