# nodus.integrations.lightning

> `NodusCallback` for a Lightning `Trainer` (ADR-103).

Source: https://nodus-platform-site.pages.dev/docs/reference/python/nodus-integrations-lightning/
Build revision: 211ad9f836655b1c3a2668c4693e442471f28614

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`NodusCallback` for a Lightning `Trainer` (ADR-103).

```python
from nodus.integrations.lightning import NodusCallback

trainer = L.Trainer(callbacks=[NodusCallback()], default_root_dir=nodus.state_dir())
trainer.fit(model, ckpt_path=NodusCallback.last_checkpoint())
```

## `NodusCallback`

```python
class NodusCallback(every_n_steps: int = 10, phase: str = 'Training') -> None
```

Metrics from `trainer.callback_metrics`, progress, phases and the checkpoint handshake.

### `NodusCallback.last_checkpoint`

```python
last_checkpoint(directory: str | os.PathLike[str] | None = None) -> str | None
```

The checkpoint this callback saved in an earlier attempt, for `trainer.fit(ckpt_path=...)`.

### `NodusCallback.on_train_batch_end`

```python
on_train_batch_end(trainer: Any, pl_module: Any, outputs: Any, batch: Any, batch_idx: int) -> None
```

### `NodusCallback.on_train_start`

```python
on_train_start(trainer: Any, pl_module: Any) -> None
```