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Source code for torchvision.datasets.folder

import os
import os.path
from typing import Any, Callable, cast, Dict, List, Optional, Tuple, Union

from PIL import Image

from .vision import VisionDataset


def has_file_allowed_extension(filename: str, extensions: Union[str, Tuple[str, ...]]) -> bool:
    """Checks if a file is an allowed extension.

    Args:
        filename (string): path to a file
        extensions (tuple of strings): extensions to consider (lowercase)

    Returns:
        bool: True if the filename ends with one of given extensions
    """
    return filename.lower().endswith(extensions if isinstance(extensions, str) else tuple(extensions))


def is_image_file(filename: str) -> bool:
    """Checks if a file is an allowed image extension.

    Args:
        filename (string): path to a file

    Returns:
        bool: True if the filename ends with a known image extension
    """
    return has_file_allowed_extension(filename, IMG_EXTENSIONS)


def find_classes(directory: str) -> Tuple[List[str], Dict[str, int]]:
    """Finds the class folders in a dataset.

    See :class:`DatasetFolder` for details.
    """
    classes = sorted(entry.name for entry in os.scandir(directory) if entry.is_dir())
    if not classes:
        raise FileNotFoundError(f"Couldn't find any class folder in {directory}.")

    class_to_idx = {cls_name: i for i, cls_name in enumerate(classes)}
    return classes, class_to_idx


def make_dataset(
    directory: str,
    class_to_idx: Optional[Dict[str, int]] = None,
    extensions: Optional[Union[str, 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).

    See :class:`DatasetFolder` for details.

    Note: The class_to_idx parameter is here optional and will use the logic of the ``find_classes`` function
    by default.
    """
    directory = os.path.expanduser(directory)

    if class_to_idx is None:
        _, class_to_idx = find_classes(directory)
    elif not class_to_idx:
        raise ValueError("'class_to_index' must have at least one entry to collect any samples.")

    both_none = extensions is None and is_valid_file is None
    both_something = extensions is not None and is_valid_file is not None
    if both_none or both_something:
        raise ValueError("Both extensions and is_valid_file cannot be None or not None at the same time")

    if extensions is not None:

        def is_valid_file(x: str) -> bool:
            return has_file_allowed_extension(x, extensions)  # type: ignore[arg-type]

    is_valid_file = cast(Callable[[str], bool], is_valid_file)

    instances = []
    available_classes = set()
    for target_class in sorted(class_to_idx.keys()):
        class_index = class_to_idx[target_class]
        target_dir = os.path.join(directory, target_class)
        if not os.path.isdir(target_dir):
            continue
        for root, _, fnames in sorted(os.walk(target_dir, followlinks=True)):
            for fname in sorted(fnames):
                path = os.path.join(root, fname)
                if is_valid_file(path):
                    item = path, class_index
                    instances.append(item)

                    if target_class not in available_classes:
                        available_classes.add(target_class)

    empty_classes = set(class_to_idx.keys()) - available_classes
    if empty_classes:
        msg = f"Found no valid file for the classes {', '.join(sorted(empty_classes))}. "
        if extensions is not None:
            msg += f"Supported extensions are: {extensions if isinstance(extensions, str) else ', '.join(extensions)}"
        raise FileNotFoundError(msg)

    return instances


[docs]class DatasetFolder(VisionDataset): """A generic data loader. This default directory structure can be customized by overriding the :meth:`find_classes` method. Args: 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 (callable, optional): 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. Attributes: classes (list): List of the class names sorted alphabetically. class_to_idx (dict): Dict with items (class_name, class_index). samples (list): List of (sample path, class_index) tuples targets (list): The class_index value for each image in the dataset """ def __init__( self, 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, ) -> None: super().__init__(root, transform=transform, target_transform=target_transform) classes, class_to_idx = self.find_classes(self.root) samples = self.make_dataset(self.root, class_to_idx, extensions, is_valid_file) self.loader = loader self.extensions = extensions self.classes = classes self.class_to_idx = class_to_idx self.samples = samples self.targets = [s[1] for s in samples]
[docs] @staticmethod def 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. Args: 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: List[Tuple[str, int]]: samples of a form (path_to_sample, class) """ if class_to_idx is None: # prevent potential bug since make_dataset() would use the class_to_idx logic of the # find_classes() function, instead of using that of the find_classes() method, which # is potentially overridden and thus could have a different logic. raise ValueError("The class_to_idx parameter cannot be None.") return make_dataset(directory, class_to_idx, extensions=extensions, is_valid_file=is_valid_file)
[docs] def find_classes(self, 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. Args: directory(str): Root directory path, corresponding to ``self.root`` Raises: FileNotFoundError: If ``dir`` has no class folders. Returns: (Tuple[List[str], Dict[str, int]]): List of all classes and dictionary mapping each class to an index. """ return find_classes(directory)
def __getitem__(self, index: int) -> Tuple[Any, Any]: """ Args: index (int): Index Returns: tuple: (sample, target) where target is class_index of the target class. """ path, target = self.samples[index] sample = self.loader(path) if self.transform is not None: sample = self.transform(sample) if self.target_transform is not None: target = self.target_transform(target) return sample, target def __len__(self) -> int: return len(self.samples)
IMG_EXTENSIONS = (".jpg", ".jpeg", ".png", ".ppm", ".bmp", ".pgm", ".tif", ".tiff", ".webp") def pil_loader(path: str) -> Image.Image: # open path as file to avoid ResourceWarning (https://github.com/python-pillow/Pillow/issues/835) with open(path, "rb") as f: img = Image.open(f) return img.convert("RGB") # TODO: specify the return type def accimage_loader(path: str) -> Any: import accimage try: return accimage.Image(path) except OSError: # Potentially a decoding problem, fall back to PIL.Image return pil_loader(path) def default_loader(path: str) -> Any: from torchvision import get_image_backend if get_image_backend() == "accimage": return accimage_loader(path) else: return pil_loader(path)
[docs]class ImageFolder(DatasetFolder): """A generic data loader where the images are arranged in this way by default: :: root/dog/xxx.png root/dog/xxy.png root/dog/[...]/xxz.png root/cat/123.png root/cat/nsdf3.png root/cat/[...]/asd932_.png This class inherits from :class:`~torchvision.datasets.DatasetFolder` so the same methods can be overridden to customize the dataset. Args: root (string): Root directory path. transform (callable, optional): A function/transform that takes in an PIL image and returns a transformed version. E.g, ``transforms.RandomCrop`` target_transform (callable, optional): A function/transform that takes in the target and transforms it. loader (callable, optional): A function to load an image given its path. is_valid_file (callable, optional): A function that takes path of an Image file and check if the file is a valid file (used to check of corrupt files) Attributes: classes (list): List of the class names sorted alphabetically. class_to_idx (dict): Dict with items (class_name, class_index). imgs (list): List of (image path, class_index) tuples """ def __init__( self, root: str, transform: Optional[Callable] = None, target_transform: Optional[Callable] = None, loader: Callable[[str], Any] = default_loader, is_valid_file: Optional[Callable[[str], bool]] = None, ): super().__init__( root, loader, IMG_EXTENSIONS if is_valid_file is None else None, transform=transform, target_transform=target_transform, is_valid_file=is_valid_file, ) self.imgs = self.samples

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