🚧 .

pytorch_lightning/core/datamodule.py

@@ -101,6 +101,12 @@ def prepare_data(self):
                 cache_imagenet()
         """
 
+    @abstractmethod
+    def setup(self, stage):
+        """
+        Use this to make assignments to the class.
+        """
+
     @abstractmethod
     def train_dataloader(self, *args, **kwargs) -> DataLoader:
         """

pytorch_lightning/trainer/model_hooks.py

@@ -1,6 +1,7 @@
 import inspect
 from abc import ABC, abstractmethod
 
+from pytorch_lightning.core.datamodule import LightningDataModule
 from pytorch_lightning.core.lightning import LightningModule
 
 
@@ -15,7 +16,9 @@ def is_function_implemented(self, f_name, model=None):
     def is_overridden(self, method_name: str, model: LightningModule = None) -> bool:
         if model is None:
             model = self.get_model()
-        super_object = LightningModule
+        # if you pass DataModule instead of None or a LightningModule, we use LightningDataModule as super
+        # TODO - refector this function to accept model_name, instance, parent so it makes more sense
+        super_object = LightningModule if not isinstance(model, LightningDataModule) else LightningDataModule
 
         # assert model, 'no model passes'
 

pytorch_lightning/trainer/trainer.py

@@ -9,6 +9,7 @@
 from torch.utils.data import DataLoader
 
 from pytorch_lightning.callbacks import ModelCheckpoint, EarlyStopping, Callback
+from pytorch_lightning.core.datamodule import LightningDataModule
 from pytorch_lightning.core.lightning import LightningModule
 from pytorch_lightning.core.memory import ModelSummary
 from pytorch_lightning.loggers import LightningLoggerBase
@@ -890,7 +891,8 @@ def fit(
             self,
             model: LightningModule,
             train_dataloader: Optional[DataLoader] = None,
-            val_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None
+            val_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
+            datamodule: Optional[LightningDataModule] = None
     ):
         r"""
         Runs the full optimization routine.
@@ -939,6 +941,7 @@ def fit(
 
         # set up the passed in dataloaders (if needed)
         self.__attach_dataloaders(model, train_dataloader, val_dataloaders)
+        self.__attach_datamodule(model, datamodule)
 
         # check that model is configured correctly
         self.check_model_configuration(model)
@@ -1111,6 +1114,24 @@ def __attach_dataloaders(self, model, train_dataloader=None, val_dataloaders=Non
         if test_dataloaders is not None:
             model.test_dataloader = _PatchDataLoader(test_dataloaders)
 
+    def __attach_datamodule(self, model, datamodule=None):
+
+        # We use datamodule if it's been provided on .fit or .test, otherwise we check model for it
+        datamodule = datamodule or getattr(model, 'datamodule', None)
+
+        # If we have a datamodule, attach necessary hooks + dataloaders
+        if datamodule:
+            if self.is_overridden('setup', datamodule):
+                model.setup = datamodule.setup
+            if self.is_overridden('prepare_data', datamodule):
+                model.prepare_data = datamodule.prepare_data
+            if self.is_overridden('train_dataloader', datamodule):
+                model.train_dataloader = datamodule.train_dataloader
+            if self.is_overridden('val_dataloader', datamodule):
+                model.val_dataloader = datamodule.val_dataloader
+            if self.is_overridden('test_dataloader', datamodule):
+                model.test_dataloader = datamodule.test_dataloader
+
     def run_pretrain_routine(self, model: LightningModule):
         """Sanity check a few things before starting actual training.
 
@@ -1241,7 +1262,8 @@ def test(
             model: Optional[LightningModule] = None,
             test_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
             ckpt_path: Optional[str] = 'best',
-            verbose: bool = True
+            verbose: bool = True,
+            datamodule: Optional[LightningDataModule] = None
     ):
         r"""
 
@@ -1305,6 +1327,9 @@ def test(
         if self.global_rank != 0:
             return
 
+        # Attach datamodule to get setup/prepare_data added to model before the call to it below
+        self.__attach_datamodule(model or self.get_model(), datamodule)
+
         self.setup('test')
 
         if model is not None: