API reference: Lightning integration

The NeptuneLogger class provided by the PyTorch Lightning library captures metadata that is generated when training models with Lightning.

Related

• For an in-depth tutorial, see Integrations ≫ Working with Lightning.
• NeptuneLogger reference in Lightning API docs
• Lightning on GitHub

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NeptuneLogger

Creates a Neptune logger for tracking metadata during a Lightning training loop.

Parameters

Name	Type	Default	Description
api_key	str, optional	None	User's Neptune API token. If None, the value of the NEPTUNE_API_TOKEN environment variable is used. To keep your token secure, avoid placing it in the source code. Instead, save it as an environment variable.
project	str, optional	None	Name of a project in the form workspace-name/project-name. If None, the value of the NEPTUNE_PROJECT environment variable is used.
name	str, optional	"Untitled"	Editable name of the run. It's displayed in the run details and can be added as a column in the runs table.
run	Run	None	An existing Run reference, as returned by neptune.init_run(). If supplied, this run will be used for logging; otherwise NeptuneLogger will create a new run for you.
log_model_checkpoints	bool, optional	True	Whether to log model checkpoints to Neptune. Works only if ModelCheckpoint is passed to the Trainer.
prefix	str, optional	"training"	Namespace under which all metadata logged by the Neptune logger will be stored.
**neptune_run_kwargs	str, optional	-	Additional keyword arguments to be passed directly to the init_run() function, such as description and tags. Works only if the run argument is set to None (that is, no existing run is passed).

Examples

If you have your Neptune credentials saved as environment variables, the following starts the Neptune logger with default settings:

from pytorch_lightning import Trainer
from pytorch_lightning.loggers import NeptuneLogger

neptune_logger = NeptuneLogger()

trainer = Trainer(logger=neptune_logger)
...

You can also pass more options to the run created by the logger:

neptune_logger = NeptuneLogger(
    project="workspace-name/project-name", # (1)!
    name="My first PTL run",
    description="Quick training run with Lightning",
    tags=["training", "resnet"],
)

1. The full project name. For example, "ml-team/classification". To copy it, navigate to the project settings → Properties.

To log metadata to the Neptune run, access the neptune_logger.experiment attribute. You can then use any logging methods from the Neptune client library to track your metadata, such as append(), assign() (=), and upload().

metadata = ...
neptune_logger.experiment["your/metadata/structure"] = metadata

You can also use the Neptune logger anywhere in your LightningModule. Access the run with the self.logger.experiment attribute:

from pytorch_lightning import LightningModule
from neptune.types import File


class LitModel(LightningModule):
    def training_step(self, batch, batch_idx):
        # log metrics
        acc = ...
        self.log("train/loss", loss)

    def any_lightning_module_function_or_hook(self):
        # Log images, using the Neptune client library
        img = ...
        self.logger.experiment["train/misclassified_imgs"].append(File.as_image(img))