How to create an iterable DataPipe with PyTorch using txt files

I have two text files to train a transformer model. However, instead of using PyTorch's own datasets, I'm using something I downloaded from the internet.

source = open('./train_de.de', encoding='utf-8').read().split('\n')
target = open('./train_en.en', encoding='utf-8').read().split('\n')

With the code above, I have some Danish sentences in a list named "source", and their translation in English sentences in another list named "target".

My question is, how can I make an iterable DataPipe with PyTorch such that when I write something like:

source, target = next(iter(train_iter))

this will give me the Danish sentence with it's corresponding English translation in seperate strings?

You can use the Dataset and DataLoader class for that.

import torch

class YourDataset(torch.utils.data.Dataset):
    def __init__(self) -> None:
        self.source = open('./train_de.de', encoding='utf-8').read().split('\n')
        self.target = open('./train_en.en', encoding='utf-8').read().split('\n')

    def __getitem__(self, idx) -> torch.Tensor:
        # load one sample by index, e.g like this:
        source_sample = self.source[idx]
        target_sample = self.target[idx]
        
        # do some preprocessing, convert to tensor and what not
        
        return source_sample, target_sample

    def __len__(self):
        return len(self.source)

Now you can create a DataLoader from your custom dataset:

yourDataset = YourDataset()
dataloader = torch.utils.data.DataLoader(
        yourDataset,
        batch_size=8,
        num_workers=0,
        shuffle=True
)

Now you can iterate through the dataloader (using a loop or next(iter(...))) and one iteration returns as many samples as your batchsize (in this case 8 stacked samples).