DatasetFolder

class torchvision.datasets.DatasetFolder(root: str, loader: Callable[[str], Any], extensions: Optional[Tuple[str, …]] = None, transform: Optional[Callable] = None, target_transform: Optional[Callable] = None, is_valid_file: Optional[Callable[[str], bool]] = None)

A generic data loader.

This default directory structure can be customized by overriding the find_classes() method.

Parameters

• root (string) – Root directory path.

• loader (callable) – A function to load a sample given its path.

• extensions (tuple[string]) – A list of allowed extensions. both extensions and is_valid_file should not be passed.

• transform (callable, optional) – A function/transform that takes in a sample and returns a transformed version. E.g, transforms.RandomCrop for images.

• target_transform (callable, optional) – A function/transform that takes in the target and transforms it.

• is_valid_file – A function that takes path of a file and check if the file is a valid file (used to check of corrupt files) both extensions and is_valid_file should not be passed.

find_classes(directory: str) → Tuple[List[str], Dict[str, int]]

Find the class folders in a dataset structured as follows:

directory/
├── class_x
│   ├── xxx.ext
│   ├── xxy.ext
│   └── ...
│       └── xxz.ext
└── class_y
    ├── 123.ext
    ├── nsdf3.ext
    └── ...
    └── asd932_.ext

This method can be overridden to only consider a subset of classes, or to adapt to a different dataset directory structure.

Parameters

directory (str) – Root directory path, corresponding to self.root

Raises

FileNotFoundError – If dir has no class folders.

Returns

List of all classes and dictionary mapping each class to an index.

Return type

(Tuple[List[str], Dict[str, int]])

static make_dataset(directory: str, class_to_idx: Dict[str, int], extensions: Optional[Tuple[str, …]] = None, is_valid_file: Optional[Callable[[str], bool]] = None) → List[Tuple[str, int]]

Generates a list of samples of a form (path_to_sample, class).

This can be overridden to e.g. read files from a compressed zip file instead of from the disk.

Parameters

• directory (str) – root dataset directory, corresponding to self.root.

• class_to_idx (Dict[str, int]) – Dictionary mapping class name to class index.

• extensions (optional) – A list of allowed extensions. Either extensions or is_valid_file should be passed. Defaults to None.

• is_valid_file (optional) – A function that takes path of a file and checks if the file is a valid file (used to check of corrupt files) both extensions and is_valid_file should not be passed. Defaults to None.

Raises

• ValueError – In case class_to_idx is empty.

• ValueError – In case extensions and is_valid_file are None or both are not None.

• FileNotFoundError – In case no valid file was found for any class.

Returns

samples of a form (path_to_sample, class)

Return type

List[Tuple[str, int]]