Attention

June 2024 Status Update: Removing DataPipes and DataLoader V2

We are re-focusing the torchdata repo to be an iterative enhancement of torch.utils.data.DataLoader. We do not plan on continuing development or maintaining the [DataPipes] and [DataLoaderV2] solutions, and they will be removed from the torchdata repo. We’ll also be revisiting the DataPipes references in pytorch/pytorch. In release torchdata==0.8.0 (July 2024) they will be marked as deprecated, and in 0.9.0 (Oct 2024) they will be deleted. Existing users are advised to pin to torchdata==0.8.0 or an older version until they are able to migrate away. Subsequent releases will not include DataPipes or DataLoaderV2. Please reach out if you suggestions or comments (please use this issue for feedback)

FlatMapper

class torchdata.datapipes.iter.FlatMapper(datapipe: IterDataPipe, fn: Optional[Callable] = None, input_col=None)

Applies a function over each item from the source DataPipe, then flattens the outputs to a single, unnested IterDataPipe (functional name: flatmap).

Note

The output from fn must be a Sequence. Otherwise, an error will be raised. If fn is None, source DataPipe will be just flattened vertically, provided that items can be unpacked.

Parameters:

• datapipe – Source IterDataPipe

• fn – the function to be applied to each element in the DataPipe, the output must be a Sequence

• input_col –

  Index or indices of data which fn is applied, such as:

  • None as default to apply fn to the data directly.

  • Integer(s) is/are used for list/tuple.

  • Key(s) is/are used for dict.

Example

>>> from torchdata.datapipes.iter import IterableWrapper
>>> def fn(e):
>>>     return [e, e * 10]
>>> source_dp = IterableWrapper(list(range(5)))
>>> flatmapped_dp = source_dp.flatmap(fn)
>>> list(flatmapped_dp)
[0, 0, 1, 10, 2, 20, 3, 30, 4, 40]
>>>
>>> source_dp = IterableWrapper([[1, 2, 3], [4, 5, 6]])
>>> flatmapped_dp = source_dp.flatmap()
>>> list(flatmapped_dp)
[1, 2, 3, 4, 5, 6]