class pytorch_lightning.cli.LightningCLI(model_class=None, datamodule_class=None, save_config_callback=<class 'pytorch_lightning.cli.SaveConfigCallback'>, save_config_kwargs=None, trainer_class=<class 'pytorch_lightning.trainer.trainer.Trainer'>, trainer_defaults=None, seed_everything_default=True, description='pytorch-lightning trainer command line tool', env_prefix='PL', env_parse=False, parser_kwargs=None, subclass_mode_model=False, subclass_mode_data=False, args=None, run=True, auto_registry=False, **kwargs)[source]

Bases: object

Implementation of a configurable command line tool for pytorch-lightning.

Receives as input pytorch-lightning classes (or callables which return pytorch-lightning classes), which are called / instantiated using a parsed configuration file and / or command line args.

Parsing of configuration from environment variables can be enabled by setting env_parse=True. A full configuration yaml would be parsed from PL_CONFIG if set. Individual settings are so parsed from variables named for example PL_TRAINER__MAX_EPOCHS.

For more info, read the CLI docs.


LightningCLI is in beta and subject to change.

  • model_class (Union[Type[LightningModule], Callable[..., LightningModule], None]) – An optional LightningModule class to train on or a callable which returns a LightningModule instance when called. If None, you can pass a registered model with --model=MyModel.

  • datamodule_class (Union[Type[LightningDataModule], Callable[..., LightningDataModule], None]) – An optional LightningDataModule class or a callable which returns a LightningDataModule instance when called. If None, you can pass a registered datamodule with --data=MyDataModule.

  • save_config_callback (Optional[Type[SaveConfigCallback]]) – A callback class to save the config.

  • save_config_kwargs (Optional[Dict[str, Any]]) – Parameters that will be used to instantiate the save_config_callback.

  • trainer_class (Union[Type[Trainer], Callable[..., Trainer]]) – An optional subclass of the Trainer class or a callable which returns a Trainer instance when called.

  • trainer_defaults (Optional[Dict[str, Any]]) – Set to override Trainer defaults or add persistent callbacks. The callbacks added through this argument will not be configurable from a configuration file and will always be present for this particular CLI. Alternatively, configurable callbacks can be added as explained in the CLI docs.

  • seed_everything_default (Union[bool, int]) – Value for the seed_everything() seed argument. Set to True to automatically choose a valid seed. Setting it to False will not call seed_everything.

  • description (str) – Description of the tool shown when running --help.

  • env_prefix (str) – Prefix for environment variables.

  • env_parse (bool) – Whether environment variable parsing is enabled.

  • parser_kwargs (Union[Dict[str, Any], Dict[str, Dict[str, Any]], None]) – Additional arguments to instantiate each LightningArgumentParser.

  • subclass_mode_model (bool) – Whether model can be any subclass of the given class.

  • subclass_mode_data (bool) –

    Whether datamodule can be any subclass of the given class.

  • args (Union[List[str], Dict[str, Any], object, None]) – Arguments to parse. If None the arguments are taken from sys.argv. Command line style arguments can be given in a list. Alternatively, structured config options can be given in a dict or jsonargparse.Namespace.

  • run (bool) – Whether subcommands should be added to run a Trainer method. If set to False, the trainer and model classes will be instantiated only.

  • auto_registry (bool) – Whether to automatically fill up the registries with all defined subclasses.


Implement to add extra arguments to the parser or link arguments.


parser (LightningArgumentParser) – The parser object to which arguments can be added

Return type:



Adds arguments from the core classes to the parser.

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Adds default arguments to the parser.

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Implement to run some code before instantiating the classes.

Return type:


static configure_optimizers(lightning_module, optimizer, lr_scheduler=None)[source]

Override to customize the configure_optimizers() method.

  • lightning_module (LightningModule) – A reference to the model.

  • optimizer (Optimizer) – The optimizer.

  • lr_scheduler (Union[_LRScheduler, ReduceLROnPlateau, None]) – The learning rate scheduler (if used).

Return type:



Method that instantiates the argument parser.

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Instantiates the classes and sets their attributes.

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Instantiates the trainer.


kwargs (Any) – Any custom trainer arguments.

Return type:


Creates argument links for optimizers and learning rate schedulers that specified a link_to.

Return type:


parse_arguments(parser, args)[source]

Parses command line arguments and stores it in self.config.

Return type:


setup_parser(add_subcommands, main_kwargs, subparser_kwargs)[source]

Initialize and setup the parser, subcommands, and arguments.

Return type:


static subcommands()[source]

Defines the list of available subcommands and the arguments to skip.

Return type:

Dict[str, Set[str]]