add mnist download utility

Author: Jaan Altosaar

data.py

@@ -0,0 +1,42 @@
+"""Get the binarized MNIST dataset and convert to hdf5.
+From https://github.com/yburda/iwae/blob/master/datasets.py
+"""
+import urllib.request
+import os
+import numpy as np
+import h5py
+
+
+def parse_binary_mnist():
+  def lines_to_np_array(lines):
+    return np.array([[int(i) for i in line.split()] for line in lines])
+  with open(os.path.join(DATASETS_DIR, 'binarized_mnist_train.amat')) as f:
+    lines = f.readlines()
+  train_data = lines_to_np_array(lines).astype('float32')
+  with open(os.path.join(DATASETS_DIR, 'binarized_mnist_valid.amat')) as f:
+    lines = f.readlines()
+  validation_data = lines_to_np_array(lines).astype('float32')
+  with open(os.path.join(DATASETS_DIR, 'binarized_mnist_test.amat')) as f:
+    lines = f.readlines()
+  test_data = lines_to_np_array(lines).astype('float32')
+  return train_data, validation_data, test_data
+
+
+def download_binary_mnist(fname):
+  DATASETS_DIR = '/tmp/'
+  subdatasets = ['train', 'valid', 'test']
+  for subdataset in subdatasets:
+    filename = 'binarized_mnist_{}.amat'.format(subdataset)
+    url = 'http://www.cs.toronto.edu/~larocheh/public/datasets/binarized_mnist/binarized_mnist_{}.amat'.format(
+        subdataset)
+    local_filename = os.path.join(DATASETS_DIR, filename)
+    urllib.request.urlretrieve(url, local_filename)
+
+  train, validation, test = parse_binary_mnist()
+  
+  data_dict = {'train': train, 'valid': validation, 'test': test}
+  f = h5py.File(fname, 'w')
+  f.create_dataset('train', data=data_dict['train'])
+  f.create_dataset('valid', data=data_dict['valid'])
+  f.create_dataset('test', data=data_dict['test'])
+  f.close()