How to Access Training Loss from Trainer Callback in Hugging Face

What Will You Learn?

Discover how to effortlessly retrieve the training loss from a callback function within the Trainer class provided by Hugging Face. Enhance your understanding of monitoring and capturing essential metrics during model training.

Introduction to the Problem and Solution

Delve into the world of extracting training loss while training a model using a custom callback with Hugging Face’s Trainer. By harnessing the power of the on_train_end method within a custom callback class attached to the Trainer instance, you can seamlessly access and store crucial information such as the training loss at different stages of the training process.

To tackle this challenge effectively, you’ll create a custom callback that logs or captures metrics throughout various phases of model training. By implementing specific methods within your custom callback class, you can retrieve and retain relevant data like the training loss for insightful analysis.


from transformers import TrainingArguments, Trainer

# Define a custom callback class inheriting from Callback
class CustomCallback:
    def __init__(self):
        self.training_loss = None

    def on_train_end(self, args, state, control, **kwargs):
        self.training_loss = state.total_training_loss / state.global_step

# Instantiate your model and trainer objects here...

# Initialize your trainer with necessary arguments including your model,
# data collator etc.
trainer_args = TrainingArguments(output_dir='./results')
trainer = Trainer(
    # Add essential arguments such as model, tokenizer, data collator...

# Train your model using trainer.train()

# Retrieve training loss after completing the training
training_loss_value = trainer.callback_handler.callbacks[0].training_loss

# Copyright PHD


  • Creating Custom Callback: Define a CustomCallback class that extends Hugging Face’s Callback.
  • Accessing Training Loss: Utilize the on_train_end method in our custom callback to compute and retain the average training loss.
  • Retrieving Loss Value: Obtain the final value of the stored training loss post completion of model training through our instantiated trainer object.
    How do I create a custom callback for extracting metrics?

    You can develop a new Python class that inherits from Hugging Face’s Callback.

    Can I access other metrics apart from just total_training_loss?

    Yes, you can enhance your custom callback implementation to capture additional metrics based on your needs.

    When is it appropriate to access these metrics during my workflow?

    Typically, accessing these metrics at significant points like after each epoch or upon completion of all epochs offers valuable insights into model performance.

    Is there any impact on performance when capturing additional metrics like this?

    While there might be minimal overhead involved depending on what you capture, it generally doesn’t significantly affect performance.

    How do I integrate these extracted metrics into my existing logging system?

    You can log these extracted metrics using popular logging libraries like TensorBoard or simply print them out for observation purposes.

    Can I visualize these captured metrics over time for analysis purposes?

    Absolutely! You can plot graphs illustrating how certain metric values evolve throughout different stages of model training.


    In conclusion, monitoring critical details such as training losses during machine learning experiments plays an integral role in enhancing models’ performance. Leveraging customized callbacks within frameworks like Hugging Face provides seamless access to vital data points throughout the modeling process. For further guidance or detailed explanations on related topics, don’t hesitate to seek assistance!

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