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| description: Explore how to use the on-train, on-validation, on-pretrain, and on-predict callbacks in Ultralytics. Learn to update params, save models, and add integration callbacks. |
| keywords: Ultralytics, Callbacks, On-train, On-validation, On-pretrain, On-predict, Parameters update, Model saving, Integration callbacks |
| --- |
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| # Reference for `ultralytics/utils/callbacks/base.py` |
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| !!! Note |
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| This file is available at [https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/base.py](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/base.py). If you spot a problem please help fix it by [contributing](https://docs.ultralytics.com/help/contributing/) a [Pull Request](https://github.com/ultralytics/ultralytics/edit/main/ultralytics/utils/callbacks/base.py) 🛠️. Thank you 🙏! |
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| ## ::: ultralytics.utils.callbacks.base.on_pretrain_routine_start |
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| ## ::: ultralytics.utils.callbacks.base.on_pretrain_routine_end |
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| ## ::: ultralytics.utils.callbacks.base.on_train_start |
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| ## ::: ultralytics.utils.callbacks.base.on_train_epoch_start |
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| ## ::: ultralytics.utils.callbacks.base.on_train_batch_start |
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| ## ::: ultralytics.utils.callbacks.base.optimizer_step |
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| <br><br> |
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| ## ::: ultralytics.utils.callbacks.base.on_before_zero_grad |
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| ## ::: ultralytics.utils.callbacks.base.on_train_batch_end |
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| ## ::: ultralytics.utils.callbacks.base.on_train_epoch_end |
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| ## ::: ultralytics.utils.callbacks.base.on_fit_epoch_end |
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| ## ::: ultralytics.utils.callbacks.base.on_model_save |
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| ## ::: ultralytics.utils.callbacks.base.on_train_end |
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| ## ::: ultralytics.utils.callbacks.base.on_params_update |
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| <br><br> |
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| ## ::: ultralytics.utils.callbacks.base.teardown |
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| ## ::: ultralytics.utils.callbacks.base.on_val_start |
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| ## ::: ultralytics.utils.callbacks.base.on_val_batch_start |
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| ## ::: ultralytics.utils.callbacks.base.on_val_batch_end |
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| ## ::: ultralytics.utils.callbacks.base.on_val_end |
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| ## ::: ultralytics.utils.callbacks.base.on_predict_start |
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| ## ::: ultralytics.utils.callbacks.base.on_predict_batch_start |
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| ## ::: ultralytics.utils.callbacks.base.on_predict_batch_end |
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| ## ::: ultralytics.utils.callbacks.base.on_predict_postprocess_end |
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| ## ::: ultralytics.utils.callbacks.base.on_predict_end |
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| ## ::: ultralytics.utils.callbacks.base.on_export_start |
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| ## ::: ultralytics.utils.callbacks.base.on_export_end |
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| ## ::: ultralytics.utils.callbacks.base.get_default_callbacks |
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| <br><br> |
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| ## ::: ultralytics.utils.callbacks.base.add_integration_callbacks |
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