Ran into "TypeError: '<' not supported between instances of 'Tensor' and 'list'" when going through dataset - machine-learning

Question

I am replicating ResNet (source: https://arxiv.org/abs/1512.03385).
I ran into the error "TypeError: '<' not supported between instances of 'Tensor' and 'list'" when trying to go through several different dataset in different sections of my code.
I tried different fixes but none worked: (i) I deleted enumerate cause I worried that using this may cause the problem (ii) I tried to go through dataloader rather than dataset but it didn't work
1st time: When I tried to view images:
for images, _ in train_loader:
print('images.shape:', images.shape)
plt.figure(figsize=(16,8))
plt.axis('off')
plt.imshow(torchvision.utils.make_grid(images, nrow=16).permute((1, 2, 0)))
break
2nd/3rd time: when I tried to validate/test the resnet:
with torch.no_grad():
for j, inputs, labels in enumerate(test_loader, start=0):
outputs = resnet_models[i](inputs)
_, prediction = torch.max(outputs, dim=1)
You may notice that I didn't run into this error when training the resnet, and the code is quite similar:
for batch, data in enumerate(train_dataloader, start=0):
inputs, labels = data
inputs, labels = inputs.to(device), labels.to(device)
Error message (taking the first error as an example. The rest is pretty much the same)
TypeError Traceback (most recent call last)
Input In [38], in <cell line: 8>()
6 print("Images AFTER NORMALIZATION")
7 print("--------------------------")
----> 8 for images, _ in training_data:
9 sort=False
10 print('images.shape:', images.shape)
File ~/miniconda3/envs/resnet/lib/python3.9/site->packages/torch/utils/data/dataset.py:471, in Subset.getitem(self, idx)
469 if isinstance(idx, list):
470 return self.dataset[[self.indices[i] for i in idx]]
--> 471 return self.dataset[self.indices[idx]]
File ~/miniconda3/envs/resnet/lib/python3.9/site->packages/torchvision/datasets/cifar.py:118, in CIFAR10.getitem(self, index)
115 img = Image.fromarray(img)
117 if self.transform is not None:
--> 118 img = self.transform(img)
120 if self.target_transform is not None:
121 target = self.target_transform(target)
File ~/miniconda3/envs/resnet/lib/python3.9/site->packages/torchvision/transforms/transforms.py:95, in Compose.call(self, img)
93 def call(self, img):
94 for t in self.transforms:
---> 95 img = t(img)
96 return img
File ~/miniconda3/envs/resnet/lib/python3.9/site->packages/torch/nn/modules/module.py:1110, in Module._call_impl(self, *input, **kwargs)
1106 # If we don't have any hooks, we want to skip the rest of the logic in
1107 # this function, and just call forward.
1108 if not (self._backward_hooks or self._forward_hooks or self._forward_pre_hooks >or _global_backward_hooks
1109 or _global_forward_hooks or _global_forward_pre_hooks):
-> 1110 return forward_call(*input, **kwargs)
1111 # Do not call functions when jit is used
1112 full_backward_hooks, non_full_backward_hooks = [], []
File ~/miniconda3/envs/resnet/lib/python3.9/site->packages/torchvision/transforms/transforms.py:707, in RandomHorizontalFlip.forward(self, >img)
699 def forward(self, img):
700 """
701 Args:
702 img (PIL Image or Tensor): Image to be flipped.
(...)
705 PIL Image or Tensor: Randomly flipped image.
706 """
--> 707 if torch.rand(1) < self.p:
708 return F.hflip(img)
709 return img
TypeError: '<' not supported between instances of 'Tensor' and 'list'

Answer 1

I was having the same error message, probably under different circumstances, but I just found my own bug and figured I would share it anyway for various readers. I was using a torchvision transformation in my dataset, which the dataloader was loading from. The transformation was
torchvision.transforms.RandomHorizontalFlip([0.5]),
and the error is that the input to this transformation should not be a list but should be
torchvision.transforms.RandomHorizontalFlip(0.5),
So if there is anything I can recommend, it's just that maybe there is some list argument being passed through that shouldn't be in some transformation or otherwise.