# tensorplay.nn.utils.rnn.unpad_sequence

Source: https://www.tensorplay.cn/docs/generated/tensorplay.nn.utils.rnn.unpad_sequence.html

```python
tensorplay.nn.utils.rnn.unpad_sequence(padded_sequences: Tensor, lengths: Tensor, batch_first: bool = False)
```

Unpad padded Tensor into a list of variable length Tensors.

unpad_sequence unstacks padded Tensor into a list of variable length Tensors.

Example

```
>>> from tensorplay.nn.utils.rnn import pad_sequence, unpad_sequence
>>> a = tp.ones(25, 300)
>>> b = tp.ones(22, 300)
>>> c = tp.ones(15, 300)
>>> sequences = [a, b, c]
>>> padded_sequences = pad_sequence(sequences)
>>> lengths = tp.as_tensor([v.size(0) for v in sequences])
>>> unpadded_sequences = unpad_sequence(padded_sequences, lengths)
>>> tp.allclose(sequences[0], unpadded_sequences[0])
True
```

Parameters:

- padded_sequences ([Tensor](/docs/generated/tensorplay.Tensor.html#tensorplay.Tensor)) – padded sequences.

- lengths ([Tensor](/docs/generated/tensorplay.Tensor.html#tensorplay.Tensor)) – length of original (unpadded) sequences.

- batch_first ([bool](https://docs.python.org/3/builtins/functions.html#bool), optional) – whether batch dimension first or not. Default: False.

Returns:

a list of Tensor objects