add typehints for torchvision.datasets.mnist (#2532)

torchvision/datasets/mnist.py

@@ -7,6 +7,7 @@ import numpy as np
 import torch
 import codecs
 import string
+from typing import Any, Callable, Dict, IO, List, Optional, Tuple, Union
 from .utils import download_url, download_and_extract_archive, extract_archive, \
     verify_str_arg
 
@@ -60,8 +61,14 @@ class MNIST(VisionDataset):
         warnings.warn("test_data has been renamed data")
         return self.data
 
-    def __init__(self, root, train=True, transform=None, target_transform=None,
-                 download=False):
+    def __init__(
+            self,
+            root: str,
+            train: bool = True,
+            transform: Optional[Callable] = None,
+            target_transform: Optional[Callable] = None,
+            download: bool = False,
+    ) -> None:
         super(MNIST, self).__init__(root, transform=transform,
                                     target_transform=target_transform)
         self.train = train  # training set or test set
@@ -79,7 +86,7 @@ class MNIST(VisionDataset):
             data_file = self.test_file
         self.data, self.targets = torch.load(os.path.join(self.processed_folder, data_file))
 
-    def __getitem__(self, index):
+    def __getitem__(self, index: int) -> Tuple[Any, Any]:
         """
         Args:
             index (int): Index
@@ -101,28 +108,28 @@ class MNIST(VisionDataset):
 
         return img, target
 
-    def __len__(self):
+    def __len__(self) -> int:
         return len(self.data)
 
     @property
-    def raw_folder(self):
+    def raw_folder(self) -> str:
         return os.path.join(self.root, self.__class__.__name__, 'raw')
 
     @property
-    def processed_folder(self):
+    def processed_folder(self) -> str:
         return os.path.join(self.root, self.__class__.__name__, 'processed')
 
     @property
-    def class_to_idx(self):
+    def class_to_idx(self) -> Dict[str, int]:
         return {_class: i for i, _class in enumerate(self.classes)}
 
-    def _check_exists(self):
+    def _check_exists(self) -> bool:
         return (os.path.exists(os.path.join(self.processed_folder,
                                             self.training_file)) and
                 os.path.exists(os.path.join(self.processed_folder,
                                             self.test_file)))
 
-    def download(self):
+    def download(self) -> None:
         """Download the MNIST data if it doesn't exist in processed_folder already."""
 
         if self._check_exists():
@@ -154,7 +161,7 @@ class MNIST(VisionDataset):
 
         print('Done!')
 
-    def extra_repr(self):
+    def extra_repr(self) -> str:
         return "Split: {}".format("Train" if self.train is True else "Test")
 
 
@@ -251,7 +258,7 @@ class EMNIST(MNIST):
         'mnist': list(string.digits),
     }
 
-    def __init__(self, root, split, **kwargs):
+    def __init__(self, root: str, split: str, **kwargs: Any) -> None:
         self.split = verify_str_arg(split, "split", self.splits)
         self.training_file = self._training_file(split)
         self.test_file = self._test_file(split)
@@ -259,14 +266,14 @@ class EMNIST(MNIST):
         self.classes = self.classes_split_dict[self.split]
 
     @staticmethod
-    def _training_file(split):
+    def _training_file(split) -> str:
         return 'training_{}.pt'.format(split)
 
     @staticmethod
-    def _test_file(split):
+    def _test_file(split) -> str:
         return 'test_{}.pt'.format(split)
 
-    def download(self):
+    def download(self) -> None:
         """Download the EMNIST data if it doesn't exist in processed_folder already."""
         import shutil
 
@@ -343,7 +350,7 @@ class QMNIST(MNIST):
         'test50k': 'test',
         'nist': 'nist'
     }
-    resources = {  # type: ignore[assignment]
+    resources: Dict[str, List[Tuple[str, str]]] = {  # type: ignore[assignment]
         'train': [('https://raw.githubusercontent.com/facebookresearch/qmnist/master/qmnist-train-images-idx3-ubyte.gz',
                    'ed72d4157d28c017586c42bc6afe6370'),
                   ('https://raw.githubusercontent.com/facebookresearch/qmnist/master/qmnist-train-labels-idx2-int.gz',
@@ -360,7 +367,10 @@ class QMNIST(MNIST):
     classes = ['0 - zero', '1 - one', '2 - two', '3 - three', '4 - four',
                '5 - five', '6 - six', '7 - seven', '8 - eight', '9 - nine']
 
-    def __init__(self, root, what=None, compat=True, train=True, **kwargs):
+    def __init__(
+            self, root: str, what: Optional[str] = None, compat: bool = True,
+            train: bool = True, **kwargs: Any
+    ) -> None:
         if what is None:
             what = 'train' if train else 'test'
         self.what = verify_str_arg(what, "what", tuple(self.subsets.keys()))
@@ -370,7 +380,7 @@ class QMNIST(MNIST):
         self.test_file = self.data_file
         super(QMNIST, self).__init__(root, train, **kwargs)
 
-    def download(self):
+    def download(self) -> None:
         """Download the QMNIST data if it doesn't exist in processed_folder already.
            Note that we only download what has been asked for (argument 'what').
         """
@@ -405,7 +415,7 @@ class QMNIST(MNIST):
         with open(os.path.join(self.processed_folder, self.data_file), 'wb') as f:
             torch.save((data, targets), f)
 
-    def __getitem__(self, index):
+    def __getitem__(self, index: int) -> Tuple[Any, Any]:
         # redefined to handle the compat flag
         img, target = self.data[index], self.targets[index]
         img = Image.fromarray(img.numpy(), mode='L')
@@ -417,15 +427,15 @@ class QMNIST(MNIST):
             target = self.target_transform(target)
         return img, target
 
-    def extra_repr(self):
+    def extra_repr(self) -> str:
         return "Split: {}".format(self.what)
 
 
-def get_int(b):
+def get_int(b: bytes) -> int:
     return int(codecs.encode(b, 'hex'), 16)
 
 
-def open_maybe_compressed_file(path):
+def open_maybe_compressed_file(path: Union[str, IO]) -> IO:
     """Return a file object that possibly decompresses 'path' on the fly.
        Decompression occurs when argument `path` is a string and ends with '.gz' or '.xz'.
     """
@@ -440,19 +450,20 @@ def open_maybe_compressed_file(path):
     return open(path, 'rb')
 
 
-def read_sn3_pascalvincent_tensor(path, strict=True):
-    """Read a SN3 file in "Pascal Vincent" format (Lush file 'libidx/idx-io.lsh').
-       Argument may be a filename, compressed filename, or file object.
-    """
-    # typemap
-    if not hasattr(read_sn3_pascalvincent_tensor, 'typemap'):
-        read_sn3_pascalvincent_tensor.typemap = {
+SN3_PASCALVINCENT_TYPEMAP = {
     8: (torch.uint8, np.uint8, np.uint8),
     9: (torch.int8, np.int8, np.int8),
     11: (torch.int16, np.dtype('>i2'), 'i2'),
     12: (torch.int32, np.dtype('>i4'), 'i4'),
     13: (torch.float32, np.dtype('>f4'), 'f4'),
-            14: (torch.float64, np.dtype('>f8'), 'f8')}
+    14: (torch.float64, np.dtype('>f8'), 'f8')
+}
+
+
+def read_sn3_pascalvincent_tensor(path: Union[str, IO], strict: bool = True) -> torch.Tensor:
+    """Read a SN3 file in "Pascal Vincent" format (Lush file 'libidx/idx-io.lsh').
+       Argument may be a filename, compressed filename, or file object.
+    """
     # read
     with open_maybe_compressed_file(path) as f:
         data = f.read()
@@ -462,14 +473,14 @@ def read_sn3_pascalvincent_tensor(path, strict=True):
     ty = magic // 256
     assert nd >= 1 and nd <= 3
     assert ty >= 8 and ty <= 14
-    m = read_sn3_pascalvincent_tensor.typemap[ty]
+    m = SN3_PASCALVINCENT_TYPEMAP[ty]
     s = [get_int(data[4 * (i + 1): 4 * (i + 2)]) for i in range(nd)]
     parsed = np.frombuffer(data, dtype=m[1], offset=(4 * (nd + 1)))
     assert parsed.shape[0] == np.prod(s) or not strict
     return torch.from_numpy(parsed.astype(m[2], copy=False)).view(*s)
 
 
-def read_label_file(path):
+def read_label_file(path: str) -> torch.Tensor:
     with open(path, 'rb') as f:
         x = read_sn3_pascalvincent_tensor(f, strict=False)
     assert(x.dtype == torch.uint8)
@@ -477,7 +488,7 @@ def read_label_file(path):
     return x.long()
 
 
-def read_image_file(path):
+def read_image_file(path: str) -> torch.Tensor:
     with open(path, 'rb') as f:
         x = read_sn3_pascalvincent_tensor(f, strict=False)
     assert(x.dtype == torch.uint8)