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101 lines
4.8 KiB
101 lines
4.8 KiB
--- |
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comments: true |
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description: Learn how to utilize callbacks in the Ultralytics framework during train, val, export, and predict modes for enhanced functionality. |
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keywords: Ultralytics, YOLO, callbacks guide, training callback, validation callback, export callback, prediction callback |
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--- |
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## Callbacks |
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Ultralytics framework supports callbacks as entry points in strategic stages of train, val, export, and predict modes. Each callback accepts a `Trainer`, `Validator`, or `Predictor` object depending on the operation type. All properties of these objects can be found in Reference section of the docs. |
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<p align="center"> |
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<br> |
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<iframe loading="lazy" width="720" height="405" src="https://www.youtube.com/embed/GsXGnb-A4Kc?start=67" |
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title="YouTube video player" frameborder="0" |
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allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" |
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allowfullscreen> |
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</iframe> |
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<br> |
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<strong>Watch:</strong> Mastering Ultralytics YOLOv8: Callbacks |
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</p> |
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## Examples |
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### Returning additional information with Prediction |
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In this example, we want to return the original frame with each result object. Here's how we can do that |
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```python |
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from ultralytics import YOLO |
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def on_predict_batch_end(predictor): |
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# Retrieve the batch data |
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_, image, _, _ = predictor.batch |
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# Ensure that image is a list |
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image = image if isinstance(image, list) else [image] |
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# Combine the prediction results with the corresponding frames |
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predictor.results = zip(predictor.results, image) |
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# Create a YOLO model instance |
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model = YOLO(f'yolov8n.pt') |
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# Add the custom callback to the model |
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model.add_callback("on_predict_batch_end", on_predict_batch_end) |
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# Iterate through the results and frames |
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for (result, frame) in model.predict(): # or model.track() |
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pass |
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``` |
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## All callbacks |
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Here are all supported callbacks. See callbacks [source code](https://github.com/ultralytics/ultralytics/blob/main/ultralytics/utils/callbacks/base.py) for additional details. |
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### Trainer Callbacks |
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| Callback | Description | |
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|-----------------------------|---------------------------------------------------------| |
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| `on_pretrain_routine_start` | Triggered at the beginning of pre-training routine | |
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| `on_pretrain_routine_end` | Triggered at the end of pre-training routine | |
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| `on_train_start` | Triggered when the training starts | |
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| `on_train_epoch_start` | Triggered at the start of each training epoch | |
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| `on_train_batch_start` | Triggered at the start of each training batch | |
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| `optimizer_step` | Triggered during the optimizer step | |
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| `on_before_zero_grad` | Triggered before gradients are zeroed | |
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| `on_train_batch_end` | Triggered at the end of each training batch | |
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| `on_train_epoch_end` | Triggered at the end of each training epoch | |
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| `on_fit_epoch_end` | Triggered at the end of each fit epoch | |
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| `on_model_save` | Triggered when the model is saved | |
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| `on_train_end` | Triggered when the training process ends | |
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| `on_params_update` | Triggered when model parameters are updated | |
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| `teardown` | Triggered when the training process is being cleaned up | |
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### Validator Callbacks |
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| Callback | Description | |
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|----------------------|-------------------------------------------------| |
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| `on_val_start` | Triggered when the validation starts | |
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| `on_val_batch_start` | Triggered at the start of each validation batch | |
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| `on_val_batch_end` | Triggered at the end of each validation batch | |
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| `on_val_end` | Triggered when the validation ends | |
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### Predictor Callbacks |
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| Callback | Description | |
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|------------------------------|---------------------------------------------------| |
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| `on_predict_start` | Triggered when the prediction process starts | |
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| `on_predict_batch_start` | Triggered at the start of each prediction batch | |
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| `on_predict_postprocess_end` | Triggered at the end of prediction postprocessing | |
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| `on_predict_batch_end` | Triggered at the end of each prediction batch | |
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| `on_predict_end` | Triggered when the prediction process ends | |
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### Exporter Callbacks |
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| Callback | Description | |
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|-------------------|------------------------------------------| |
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| `on_export_start` | Triggered when the export process starts | |
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| `on_export_end` | Triggered when the export process ends |
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