'DataLoader' object does not support indexing

python computer-vision pytorch imagenet

15,495

Solution 1

Solution

input_transform = standard_transforms.Compose([
    transforms.Resize((255,255)), # to Make sure all the 
    transforms.CenterCrop(224),   # imgs are at the same size 
    transforms.ToTensor()
])  


# torch.utils.data.Dataset object
trainset = datasets.ImageNet('/media/farshid/DataStore/temp/Imagenet/',
                             split='train', download=False, transform = input_transform)
# torch.utils.data.DataLoader object
trainloader =torch.utils.data.DataLoader(trainset, batch_size=2, shuffle=False)


for batch_idx, data in enumerate(trainloader, 0):
    x, y = data 
    break

Solution 2

Well, the answer is pretty simple (besides error mentioned in the other answer).

DataLoader has no __getitem__ method (see in the source code for yourself).

It is used for iterating, not random access, over data (or batches of data). If you want to access specific element you should use torch.utils.data.Dataset, in your case:

trainset = torchvision.datasets.ImageNet('/media/farshid/DataStore/temp/Imagenet/', split='train', )
trainset[0]

Getting a batch

If you want to get a batch you may iterate over it and break afterwards:

for batch in dataloader:
    print(batch) # or anything else you want to do
    break

DataLoader creates random indices in default or specified way (see samplers), hence there is no __getitem__ as it wouldn't make sense for this object.

You may also inherit from the DataLoader and create your own __getitem__ function doing what you want (more complicated though).

Full example

# torch.utils.data.Dataset object
trainset = datasets.ImageNet('/media/farshid/DataStore/temp/Imagenet/', split='train', download=True)
# torch.utils.data.DataLoader object
trainloader =torch.utils.data.DataLoader(trainset, batch_size=1, shuffle=False)

for batch in trainloader:
    print(batch)
    break

Above should print the first batch whatever is inside.

Solution 3

The input dataset to torch.utils.data.DataLoader() should be of type torch.utils.data.Dataset, not torch.utils.data.DataLoader, which is what you are doing in above code.

So, your above code should be:

trainset = torchvision.datasets.ImageNet('/media/farshid/DataStore/temp/Imagenet/', 
                                          split='train', 
                                          download=False)

trainloader = torch.utils.data.DataLoader(trainset, 
                                          batch_size=1, 
                                          shuffle=False, 
                                          num_workers=1)

For more details, check the official torch documentation here.

15,495

Author by

Farshid Rayhan

Hit me up if you want to collaborate on a computer vision project I will be more than happy to provide contribution.

Updated on June 05, 2022

Comments

Farshid Rayhan almost 2 years
I have downloaded the ImageNet dataset via this pytorch api by setting download=True. But I cannot iterate through the dataloader.

The error says "'DataLoader' object does not support indexing"
```
trainset = torch.utils.data.DataLoader(
    datasets.ImageNet('/media/farshid/DataStore/temp/Imagenet/', split='train',
                      download=False))
trainloader = torch.utils.data.DataLoader(trainset, batch_size=1, shuffle=False, num_workers=1)
```
I tried a simple approach I just tried to run the following,
```
trainloader[0]
```
In the root directory, the pattern is
```
root/  
    train/  
          n01440764/
          n01443537/ 
                   n01443537_2.jpg
```
The docs in the official website doesnt say anything else. https://pytorch.org/docs/stable/torchvision/datasets.html#imagenet

What am I doing wrong ?
Farshid Rayhan almost 5 years

Yes I see the problem and I tried your solution. I still have the same error "'DataLoader' object does not support indexing" when I do "trainloader[0]"
Szymon Maszke almost 5 years

While true, it does not solve the issue (leaving alone the fact of reiterating the comment).
Farshid Rayhan almost 5 years

Then how do I get it like a batch ?
Farshid Rayhan almost 5 years

Just to clarify, what do you mean by 'dataloader' according to Anubhav Singh's code is it the 'trainset' or 'trainloader' ? Cause with trainloader it doesnt work !
Szymon Maszke almost 5 years

It works if you create DataLoader from train_dataset. dataloader refers to instance of such DataLoader class.
Farshid Rayhan almost 5 years

I am really getting confused here. Can you please explain or just update your codes
Farshid Rayhan almost 5 years

Well yes and no. The problem I was facing was the img being a PIL file and the debugger doesnt say it. Your code still doesnt run without errors. The fix is add "standard_transforms.ToTensor()," as transforms. :)
Farshid Rayhan almost 5 years

Plus for some reason increasing the batch size from 1 to anything else doesnt work
Szymon Maszke almost 5 years

Yeah, I assumed correct transformations and print is a simple example to get the point across.