mnist dataset download setting

tutorial-contents/401_CNN.py

@@ -7,6 +7,11 @@ torch: 0.1.11
 torchvision
 matplotlib
 """
+# library
+# standard library
+import os
+
+# third-party library
 import torch
 import torch.nn as nn
 from torch.autograd import Variable
@@ -20,16 +25,20 @@ torch.manual_seed(1)    # reproducible
 EPOCH = 1               # train the training data n times, to save time, we just train 1 epoch
 BATCH_SIZE = 50
 LR = 0.001              # learning rate
-DOWNLOAD_MNIST = True   # set to False if you have downloaded
+DOWNLOAD_MNIST = False
 
 
 # Mnist digits dataset
+if not(os.path.exists('./mnist/')) or not os.listdir('./mnist/'):
+    # not mnist dir or mnist is empyt dir
+    DOWNLOAD_MNIST = True
+
 train_data = torchvision.datasets.MNIST(
     root='./mnist/',
     train=True,                                     # this is training data
     transform=torchvision.transforms.ToTensor(),    # Converts a PIL.Image or numpy.ndarray to
                                                     # torch.FloatTensor of shape (C x H x W) and normalize in the range [0.0, 1.0]
-    download=DOWNLOAD_MNIST,                        # download it if you don't have it
+    download=DOWNLOAD_MNIST,
 )
 
 # plot one example