standalone val (#56)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/engine/trainer.py

@@ -25,7 +25,7 @@ import ultralytics.yolo.utils as utils
 import ultralytics.yolo.utils.callbacks as callbacks
 from ultralytics.yolo.data.utils import check_dataset, check_dataset_yaml
 from ultralytics.yolo.utils import LOGGER, ROOT, TQDM_BAR_FORMAT, colorstr
-from ultralytics.yolo.utils.checks import print_args
+from ultralytics.yolo.utils.checks import check_file, print_args
 from ultralytics.yolo.utils.files import increment_path, save_yaml
 from ultralytics.yolo.utils.modeling import get_model
 from ultralytics.yolo.utils.torch_utils import ModelEMA, de_parallel, init_seeds, one_cycle, strip_optimizer
@@ -299,13 +299,16 @@ class BaseTrainer:
         """
         Get train, val path from data dict if it exists. Returns None if data format is not recognized
         """
-        return data["train"], data["val"]
+        return data["train"], data.get("val") or data.get("test")
 
     def get_model(self, model: Union[str, Path]):
         """
         load/create/download model for any task
         """
-        pretrained = not str(model).endswith(".yaml")
+        pretrained = True
+        if str(model).endswith(".yaml"):
+            model = check_file(model)
+            pretrained = False
         return self.load_model(model_cfg=None if pretrained else model,
                                weights=get_model(model) if pretrained else None,
                                data=self.data)  # model
@@ -376,7 +379,7 @@ class BaseTrainer:
         """
         To set or update model parameters before training.
         """
-        pass
+        self.model.names = self.data["names"]
 
     def build_targets(self, preds, targets):
         pass