huggingface--transformers/docs/source/en/main_classes/callback.md

Callbacks

Callbacks are objects that can customize the behavior of the training loop in the PyTorch [Trainer] that can inspect the training loop state (for progress reporting, logging on TensorBoard or other ML platforms...) and take decisions (like early stopping).

Callbacks are "read only" pieces of code, apart from the [TrainerControl] object they return, they cannot change anything in the training loop. For customizations that require changes in the training loop, you should subclass [Trainer] and override the methods you need (see trainer for examples).

By default, TrainingArguments.report_to is set to "none".

The main class that implements callbacks is [TrainerCallback]. It gets the [TrainingArguments] used to instantiate the [Trainer], can access that Trainer's internal state via [TrainerState], and can take some actions on the training loop via [TrainerControl].

Available Callbacks

Here is the list of the available [TrainerCallback] in the library:

autodoc integrations.CometCallback - setup

autodoc DefaultFlowCallback

autodoc PrinterCallback

autodoc ProgressCallback

autodoc EarlyStoppingCallback

autodoc integrations.TensorBoardCallback

autodoc integrations.TrackioCallback - setup

autodoc integrations.WandbCallback - setup

autodoc integrations.MLflowCallback - setup

autodoc integrations.AzureMLCallback

autodoc integrations.CodeCarbonCallback

autodoc integrations.ClearMLCallback

autodoc integrations.DagsHubCallback

autodoc integrations.FlyteCallback

autodoc integrations.KubeflowCallback

autodoc integrations.DVCLiveCallback - setup

autodoc integrations.SwanLabCallback - setup

TrainerCallback

autodoc TrainerCallback

Here is an example of how to register a custom callback with the PyTorch [Trainer]:

class MyCallback(TrainerCallback):
    "A callback that prints a message at the beginning of training"

    def on_train_begin(self, args, state, control, **kwargs):
        print("Starting training")


trainer = Trainer(
    model,
    args,
    train_dataset=train_dataset,
    eval_dataset=eval_dataset,
    callbacks=[MyCallback],  # We can either pass the callback class this way or an instance of it (MyCallback())
)

Another way to register a callback is to call trainer.add_callback() as follows:

trainer = Trainer(...)
trainer.add_callback(MyCallback)
# Alternatively, we can pass an instance of the callback class
trainer.add_callback(MyCallback())

TrainerState

autodoc TrainerState

TrainerControl

autodoc TrainerControl