torch.narrow — PyTorch 2.7 documentation (original) (raw)

torch.narrow(input, dim, start, length) → Tensor¶

Returns a new tensor that is a narrowed version of input tensor. The dimension dim is input from start to start + length. The returned tensor and input tensor share the same underlying storage.

Parameters

• input (Tensor) – the tensor to narrow
• dim (int) – the dimension along which to narrow
• start (int or Tensor) – index of the element to start the narrowed dimension from. Can be negative, which means indexing from the end of dim. IfTensor, it must be an 0-dim integral Tensor (bools not allowed)
• length (int) – length of the narrowed dimension, must be weakly positive

Example:

x = torch.tensor([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) torch.narrow(x, 0, 0, 2) tensor([[ 1, 2, 3], [ 4, 5, 6]]) torch.narrow(x, 1, 1, 2) tensor([[ 2, 3], [ 5, 6], [ 8, 9]]) torch.narrow(x, -1, torch.tensor(-1), 1) tensor([[3], [6], [9]])