TypeError: expected str, bytes or os.PathLike object, not NoneType (YOLO)

Question

So, I'm trying to train a YOLO classification model on a custom dataset that contains jpg-images of two different classes. But when I launch training, I get following error:

Traceback (most recent call last):
  File "C:\pythonProject\main.py", line 5, in <module>
    model.train(data='./training_dataset', epochs=1, imgsz=64)
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\engine\model.py", line 341, in train
    self.trainer.train()
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\engine\trainer.py", line 192, in train
    self._do_train(world_size)
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\engine\trainer.py", line 288, in _do_train
    self._setup_train(world_size)
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\engine\trainer.py", line 255, in _setup_train
    self.test_loader = self.get_dataloader(self.testset, batch_size=batch_size * 2, rank=-1, mode='val')
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\models\yolo\classify\train.py", line 88, in get_dataloader
    dataset = self.build_dataset(dataset_path, mode)
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\models\yolo\classify\train.py", line 83, in build_dataset
    return ClassificationDataset(root=img_path, args=self.args, augment=mode == 'train', prefix=mode)
  File "C:\pythonProject\venv\lib\site-packages\ultralytics\data\dataset.py", line 220, in __init__
    super().__init__(root=root)
  File "C:\pythonProject\venv\lib\site-packages\torchvision\datasets\folder.py", line 309, in __init__
    super().__init__(
  File "C:\pythonProject\venv\lib\site-packages\torchvision\datasets\folder.py", line 145, in __init__
    samples = self.make_dataset(self.root, class_to_idx, extensions, is_valid_file)
  File "C:\pythonProject\venv\lib\site-packages\torchvision\datasets\folder.py", line 189, in make_dataset
    return make_dataset(directory, class_to_idx, extensions=extensions, is_valid_file=is_valid_file)
  File "C:\pythonProject\venv\lib\site-packages\torchvision\datasets\folder.py", line 61, in make_dataset
    directory = os.path.expanduser(directory)
  File "C:\Users\User\AppData\Local\Programs\Python\Python310\lib\ntpath.py", line 293, in expanduser
    path = os.fspath(path)
TypeError: expected str, bytes or os.PathLike object, not NoneType

I've tried two different datasets and that problem occured on both of them.

My full code:

from ultralytics import YOLO

model = YOLO('yolov8n-cls.pt')

model.train(data='./training_dataset', epochs=1, imgsz=64)

Dataset structure:

training_dataset/train/cats;

training_dataset/train/dogs

Answer 1

Nvm, the problem was that my dataset did not contain 'test' folder which is crucial for that model. After I added it, everything worked just fine.

So, your dataset must have following structure:

dataset/
|
|-- train/
|   |-- class1/
|   |   |-- class1_1.png
|   |   |-- class1_2.png
|   |   |-- ...
|   |
|   |-- class2/
|   |   |-- class2_1.png
|   |   |-- class2_2.png
|   |   |-- ...
|   |
|
|
|-- test/
|   |-- class1/
|   |   |-- class1_1.png
|   |   |-- class1_2.png
|   |   |-- ...
|   |
|   |-- class2/
|   |   |-- class2_1.png
|   |   |-- class2_2.png
|   |   |-- ...
|   |