Merge pull request #1112 from zym1010/issue1083

fix #1083

tutorials/image/cifar10/cifar10.py

@@ -394,5 +394,6 @@ def maybe_download_and_extract():
     print()
     statinfo = os.stat(filepath)
     print('Successfully downloaded', filename, statinfo.st_size, 'bytes.')
-
-  tarfile.open(filepath, 'r:gz').extractall(dest_directory)
+  extracted_dir_path = os.path.join(dest_directory, 'cifar-10-batches-bin')
+  if not os.path.exists(extracted_dir_path):
+    tarfile.open(filepath, 'r:gz').extractall(dest_directory)