Add callback system + associated test

pytorch_lightning/__init__.py

@@ -29,10 +29,12 @@
 
     from .core import data_loader, LightningModule
     from .trainer import Trainer
+    from .callbacks import Callback
 
     __all__ = [
         'Trainer',
         'LightningModule',
+        'Callback',
         'data_loader',
     ]
     # __call__ = __all__

pytorch_lightning/callbacks/base.py

@@ -22,11 +22,39 @@ def trainer(self):
         assert self._trainer is not None, _NO_TRAINER_ERROR_MSG
         return self._trainer
 
+    @property
+    def default_save_path(self):
+        """Trainer default save path.
+        """
+        return self._trainer.default_save_path
+
+    @property
+    def rank(self):
+        """Current trainer rank.
+        """
+        return self._trainer.proc_rank
+
     def set_trainer(self, trainer):
         """Make a link to the trainer, so different things like `trainer.current_epoch`,
         `trainer.batch_idx`, `trainer.global_step` can be used."""
         self._trainer = trainer
 
+    def on_init_begin(self):
+        """Called when the trainer initialization begins."""
+        pass
+
+    def on_init_end(self):
+        """Called when the trainer initialization ends."""
+        pass
+
+    def on_fit_begin(self):
+        """Called when the fit begins."""
+        pass
+
+    def on_fit_end(self):
+        """Called when the fit ends."""
+        pass
+
     def on_epoch_begin(self):
         """Called when the epoch begins."""
         pass

pytorch_lightning/trainer/callback_hook.py

@@ -0,0 +1,82 @@
+from abc import ABC
+
+from pytorch_lightning.callbacks import Callback
+
+
+class TrainerCallbackHookMixin(ABC):
+
+    def __init__(self):
+        # this is just a summary on variables used in this abstract class,
+        # the proper values/initialisation should be done in child class
+        self.callbacks: list[Callback] = []
+
+    def on_init_begin(self):
+        """Called when the trainer initialization begins."""
+        for callback in self.callbacks:
+            callback.set_trainer(self)
+            callback.on_init_begin()
+
+    def on_init_end(self):
+        """Called when the trainer initialization ends."""
+        for callback in self.callbacks:
+            callback.on_init_end()
+
+    def on_fit_begin(self):
+        """Called when the fit begins."""
+        for callback in self.callbacks:
+            callback.on_fit_begin()
+
+    def on_fit_end(self):
+        """Called when the fit ends."""
+        for callback in self.callbacks:
+            callback.on_fit_end()
+
+    def on_epoch_begin(self):
+        """Called when the epoch begins."""
+        for callback in self.callbacks:
+            callback.on_epoch_begin()
+
+    def on_epoch_end(self):
+        """Called when the epoch ends."""
+        for callback in self.callbacks:
+            callback.on_epoch_end()
+
+    def on_train_begin(self):
+        """Called when the train begins."""
+        for callback in self.callbacks:
+            callback.on_train_begin()
+
+    def on_train_end(self):
+        """Called when the train ends."""
+        for callback in self.callbacks:
+            callback.on_train_end()
+
+    def on_batch_begin(self):
+        """Called when the training batch begins."""
+        for callback in self.callbacks:
+            callback.on_batch_begin()
+
+    def on_batch_end(self):
+        """Called when the training batch ends."""
+        for callback in self.callbacks:
+            callback.on_batch_end()
+
+    def on_validation_begin(self):
+        """Called when the validation loop begins."""
+        for callback in self.callbacks:
+            callback.on_validation_begin()
+
+    def on_validation_end(self):
+        """Called when the validation loop ends."""
+        for callback in self.callbacks:
+            callback.on_validation_end()
+
+    def on_test_begin(self):
+        """Called when the test begins."""
+        for callback in self.callbacks:
+            callback.on_test_begin()
+
+    def on_test_end(self):
+        """Called when the test ends."""
+        for callback in self.callbacks:
+            callback.on_test_end()

pytorch_lightning/trainer/evaluation_loop.py

@@ -123,6 +123,8 @@
 
 """
 
+from typing import Callable
+
 import sys
 from abc import ABC, abstractmethod
 
@@ -169,6 +171,12 @@ def __init__(self):
         self.get_val_dataloaders = None
         self.use_tpu = None
 
+        # Callback system
+        self.on_validation_begin: Callable = None
+        self.on_validation_end: Callable = None
+        self.on_test_begin: Callable = None
+        self.on_test_end: Callable = None
+
     @abstractmethod
     def copy_trainer_model_properties(self, model):
         # this is just empty shell for code from other class
@@ -293,6 +301,12 @@ def run_evaluation(self, test=False):
                     Please define and try again'''
             raise MisconfigurationException(m)
 
+        # Validation/Test begin callbacks
+        if test:
+            self.on_test_begin()
+        else:
+            self.on_validation_begin()
+
         # hook
         model = self.get_model()
         model.on_pre_performance_check()
@@ -353,6 +367,12 @@ def run_evaluation(self, test=False):
         if self.proc_rank == 0 and self.checkpoint_callback is not None and not test:
             self.checkpoint_callback.on_validation_end()
 
+        # Validation/Test end callbacks
+        if test:
+            self.on_test_end()
+        else:
+            self.on_validation_end()
+
     def evaluation_forward(self, model, batch, batch_idx, dataloader_idx, test=False):
         # make dataloader_idx arg in validation_step optional
         args = [batch, batch_idx]

pytorch_lightning/trainer/trainer.py

@@ -30,8 +30,10 @@
 from pytorch_lightning.trainer.training_io import TrainerIOMixin
 from pytorch_lightning.trainer.training_loop import TrainerTrainLoopMixin
 from pytorch_lightning.trainer.training_tricks import TrainerTrainingTricksMixin
+from pytorch_lightning.trainer.callback_hook import TrainerCallbackHookMixin
 from pytorch_lightning.utilities.debugging import MisconfigurationException
 from pytorch_lightning.profiler import Profiler, PassThroughProfiler
+from pytorch_lightning.callbacks import Callback
 
 
 try:
@@ -62,13 +64,15 @@ class Trainer(TrainerIOMixin,
               TrainerEvaluationLoopMixin,
               TrainerTrainLoopMixin,
               TrainerCallbackConfigMixin,
+              TrainerCallbackHookMixin
               ):
 
     def __init__(
             self,
             logger: Union[LightningLoggerBase, bool] = True,
             checkpoint_callback: Union[ModelCheckpoint, bool] = True,
             early_stop_callback: Optional[Union[EarlyStopping, bool]] = None,
+            callbacks: list = [],
             default_save_path: Optional[str] = None,
             gradient_clip_val: float = 0,
             gradient_clip=None,  # backward compatible, todo: remove in v0.8.0
@@ -168,6 +172,18 @@ def __init__(
 
                     trainer = Trainer(early_stop_callback=early_stop_callback)
 
+            callback (:class:`.Callback`): Add a list of callbacks.
+                Example::
+                    from pytorch_lightning.callbacks import Callback
+                    class PrintCallback(Callback):
+                        def on_train_begin(self):
+                            print("Training is started!")
+                        def on_train_end(self):
+                            print(f"Training is done. The logs are: {self.trainer.logs}")
+                    # a list of callbacks
+                    callbacks = [PrintCallback()]
+                    trainer = Trainer(callbacks=callbacks)
+
             default_save_path: Default path for logs and weights when no logger/ckpt_callback passed
                 Example::
 
@@ -584,6 +600,10 @@ def __init__(
 
         """
 
+        # Init callbacks
+        self.callbacks = callbacks
+        self.on_init_begin()
+
         # Transfer params
         # Backward compatibility
         if nb_gpu_nodes is not None:
@@ -766,6 +786,9 @@ def __init__(
             use_amp = True
         self.init_amp(use_amp)
 
+        # Callback system
+        self.on_init_end()
+
     @property
     def slurm_job_id(self) -> int:
         try:
@@ -901,6 +924,9 @@ def fit(
         _set_dataloader(model, val_dataloader, 'val_dataloader')
         _set_dataloader(model, test_dataloader, 'test_dataloader')
 
+        # Fit begin callbacks
+        self.on_fit_begin()
+
         # when using multi-node or DDP within a node start each module in a separate process
         if self.use_ddp2:
             task = int(os.environ['SLURM_LOCALID'])
@@ -940,6 +966,9 @@ def fit(
 
             self.run_pretrain_routine(model)
 
+        # Fit end callbacks
+        self.on_fit_end()
+
         # return 1 when finished
         # used for testing or when we need to know that training succeeded
         return 1
@@ -1034,8 +1063,8 @@ def run_pretrain_routine(self, model: LightningModule):
             return
 
         # check if we should run validation during training
-        self.disable_validation = ((self.num_val_batches == 0 or
-                                    not self.is_overriden('validation_step')) and
+        self.disable_validation = ((self.num_val_batches == 0
+                                    or not self.is_overriden('validation_step')) and
                                    not self.fast_dev_run)
 
         # run tiny validation (if validation defined)
@@ -1139,7 +1168,7 @@ def _set_dataloader(model, dataloader, attribute):
         if is_dataloader or is_dataloader_list and valid_loaders:
 
             # Overwrite abstract methods
-            dl = lambda: dataloader
+            def dl(): return dataloader
             dl.__name__ = attribute
             setattr(model, attribute, dl)