Utilize DownloadableDataset (#27)

* Rewrite mnist_dataset to use DownloadableDataset

* Remove abstract methods from mnist_dataset

Author: SvecDavid

mnist_convnet/mnist_dataset.py

@@ -1,7 +1,6 @@
 import logging
 import gzip
 import struct
-import urllib.request
 import os
 import os.path as path
 
@@ -15,12 +14,13 @@
              'test_labels': 't10k-labels-idx1-ubyte.gz'}
 
 
-class MNISTDataset(cx.BaseDataset):
+class MNISTDataset(cx.DownloadableDataset):
     """ MNIST dataset for hand-written digits recognition."""
 
-    def _configure_dataset(self, data_root=path.join('datasets', '.mnist-data'), batch_size:int=100, **kwargs) -> None:
+    def _configure_dataset(self, data_root=path.join('mnist_convnet', '.mnist-data'), batch_size:int=100, **kwargs) -> None:
         self._batch_size = batch_size
         self._data_root = data_root
+        self._download_urls = [path.join(DOWNLOAD_ROOT, filename) for filename in FILENAMES.values()]
         self._data = {}
         self._data_loaded = False
 
@@ -52,14 +52,3 @@ def test_stream(self) -> cx.Stream:
         for i in range(0, len(self._data['test_labels']), self._batch_size):
             yield {'images': self._data['test_images'][i: i + self._batch_size],
                    'labels': self._data['test_labels'][i: i + self._batch_size]}
-
-    def download(self) -> None:
-        """Download method may be invoked with `cxflow dataset download <path-to-config>`."""
-        for part in FILENAMES.values():
-            target = path.join(self._data_root, part)
-            if path.exists(target):
-                logging.info('\t%s already exists', target)
-            else:
-                os.makedirs(self._data_root, exist_ok=True)
-                logging.info('\tdownloading %s', target)
-                urllib.request.urlretrieve(DOWNLOAD_ROOT+part, target)