flatten Wandb hyperparameters dict (#2459)

* wandb logging fix

* Changelog fix

* change test

Author: anthonytec2

CHANGELOG.md

@@ -21,6 +21,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
+- Flattening Wandb Hyperparameters ([#2459](https://github.com/PyTorchLightning/pytorch-lightning/pull/2459))
+
 - Fixed using the same DDP python interpreter and actually running ([#2482](https://github.com/PyTorchLightning/pytorch-lightning/pull/2482))
 
 - Fixed model summary input type conversion for models that have input dtype different from model parameters ([#2510](https://github.com/PyTorchLightning/pytorch-lightning/pull/2510))

pytorch_lightning/loggers/wandb.py

@@ -125,6 +125,7 @@ def watch(self, model: nn.Module, log: str = 'gradients', log_freq: int = 100):
     @rank_zero_only
     def log_hyperparams(self, params: Union[Dict[str, Any], Namespace]) -> None:
         params = self._convert_params(params)
+        params = self._flatten_dict(params)
         self.experiment.config.update(params, allow_val_change=True)
 
     @rank_zero_only

tests/loggers/test_wandb.py

@@ -19,9 +19,12 @@ def test_wandb_logger(wandb):
     logger.log_metrics({'acc': 1.0}, step=3)
     wandb.init().log.assert_called_once_with({'global_step': 3, 'acc': 1.0})
 
-    logger.log_hyperparams({'test': None})
-    wandb.init().config.update.assert_called_once_with({'test': None}, allow_val_change=True)
-
+    logger.log_hyperparams({'test': None, 'nested': {'a': 1}, 'b': [2, 3, 4]})
+    wandb.init().config.update.assert_called_once_with(
+        {'test': 'None', 'nested/a': 1, 'b': [2, 3, 4]},
+        allow_val_change=True,
+    )
+    
     logger.watch('model', 'log', 10)
     wandb.init().watch.assert_called_once_with('model', log='log', log_freq=10)