Traceback (most recent call last) in Colab when looping through dataloader in pytorch
I'm working on a project to classify flower images using a pre-trained model vgg19 using pytorch.

I'm relying on the model features only and using a custom classifier.

However on starting a for-loop to feed images to the model classifier and calculate accuracy through epochs I get an error.

I'm not sure what's the problem as the error is a traceback (most recent call last)

Below is my notebook.

The cell throwing the error is below

#training the classifier
criterion = nn.CrossEntropyLoss()
optimizer = optim.SGD(model.classifier.parameters(),lr=0.01)

steps = 0
running_loss = 0
epochs = 5
print_every = 5

for epoch in range(epochs):
    for images,labels in train_dataloader:
        steps += 1
        optimizer.zero_grad()

        logps = model.forward(images)
        loss  = criterion(logps,labels)
        loss.backward()
        optimizer.step()

        running_loss += loss.item()

        if steps % print_every == 0:
            test_loss = 0
            accuracy = 0
            model.eval()

            with torch.no_grad():
                for images, labels in valid_dataloader:
                    logps = model.forward(images)
                    batch_loss = criterion(logps, labels)

                    test_loss += batch_loss.item()

                    #Calculate accuracy
                    ps = torch.exp(logps)
                    top_p, top_class = ps.topk(5,dim=1)
                    equals = top_class  == labels.view(*top_class.shape)
                    accuracy += torch.mean(equals.type(torch.FloatTensor)).item()

            print(f"Epoch {epoch+1}/{epochs}.."
             f"Train loss: {running_loss/print_every: .3f}.."
             f"Test loss: {test_loss/len(valid_loader):.3f}.."
             f"Test accuracy: {accuracy/len(valid_loader):.3f}")
            running_loss = 0
            model.train()


The error I get on running the notebook 

AttributeError                            Traceback (most recent call last)
&lt;ipython-input-11-c218f8f2b72e&gt; in &lt;module&gt;()
      8 
      9 for epoch in range(epochs):
---&gt; 10     for images,labels in train_dataloader:
     11         steps += 1
     12         optimizer.zero_grad()

/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataloader.py in __next__(self)
    312         if self.num_workers == 0:  # same-process loading
    313             indices = next(self.sample_iter)  # may raise StopIteration
--&gt; 314             batch = self.collate_fn([self.dataset[i] for i in indices])
    315             if self.pin_memory:
    316                 batch = pin_memory_batch(batch)

/usr/local/lib/python3.6/dist-packages/torch/utils/data/dataloader.py in &lt;listcomp&gt;(.0)
    312         if self.num_workers == 0:  # same-process loading
    313             indices = next(self.sample_iter)  # may raise StopIteration
--&gt; 314             batch = self.collate_fn([self.dataset[i] for i in indices])
    315             if self.pin_memory:
    316                 batch = pin_memory_batch(batch)

/usr/local/lib/python3.6/dist-packages/torchvision/datasets/folder.py in __getitem__(self, index)
     99         """
    100         path, target = self.samples[index]
--&gt; 101         sample = self.loader(path)
    102         if self.transform is not None:
    103             sample = self.transform(sample)

/usr/local/lib/python3.6/dist-packages/torchvision/datasets/folder.py in default_loader(path)
    145         return accimage_loader(path)
    146     else:
--&gt; 147         return pil_loader(path)
    148 
    149 

/usr/local/lib/python3.6/dist-packages/torchvision/datasets/folder.py in pil_loader(path)
    127     # open path as file to avoid ResourceWarning (https://github.com/python-pillow/Pillow/issues/835)
    128     with open(path, 'rb') as f:
--&gt; 129         img = Image.open(f)
    130         return img.convert('RGB')
    131 

/usr/local/lib/python3.6/dist-packages/PIL/Image.py in open(fp, mode)
   2319     return True
   2320 
-&gt; 2321 
   2322 def new(mode, size, color=0):
   2323     """

/usr/local/lib/python3.6/dist-packages/PIL/Image.py in preinit()
    368 
    369 
--&gt; 370 def preinit():
    371     """Explicitly load standard file format drivers."""
    372 

/usr/local/lib/python3.6/dist-packages/PIL/PpmImagePlugin.py in &lt;module&gt;()
    156 Image.register_save(PpmImageFile.format, _save)
    157 
--&gt; 158 Image.register_extensions(PpmImageFile.format, [".pbm", ".pgm", ".ppm"])

AttributeError: module 'PIL.Image' has no attribute 'register_extensions'


The error is caused because of interference created by the older version of Pillow which is already installed on Colab. You need to upgrade it to the latest version. Use the following code to upgrade to the latest version of Pillow.

!pip uninstall -y Pillow
!pip install Pillow==5.3.0
import PIL.Image


Now, simply restart the Restart the runtime. It'll remove the error.
