<br />

|---|
| [![](https://www.tensorflow.org/images/GitHub-Mark-32px.png) View source on GitHub](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/learning_rate_scheduler.py#L9-L102) |

Learning rate scheduler.

Inherits From: [`Callback`](https://www.tensorflow.org/api_docs/python/tf/keras/callbacks/Callback)

    tf.keras.callbacks.LearningRateScheduler(
        schedule, verbose=0
    )

### Used in the notebooks

| Used in the tutorials |
|---|
| - [Distributed training with Keras](https://www.tensorflow.org/tutorials/distribute/keras) - [TensorBoard Scalars: Logging training metrics in Keras](https://www.tensorflow.org/tensorboard/scalars_and_keras) |

At the beginning of every epoch, this callback gets the updated learning
rate value from `schedule` function provided at `__init__`, with the current
epoch and current learning rate, and applies the updated learning rate on
the optimizer.

<br />

<br />

<br />

| ## Args ||
|---|---|
| `schedule` | A function that takes an epoch index (integer, indexed from 0) and current learning rate (float) as inputs and returns a new learning rate as output (float). |
| `verbose` | Integer. 0: quiet, 1: log update messages. |

<br />

#### Example:

    # This function keeps the initial learning rate for the first ten epochs
    # and decreases it exponentially after that.
    def scheduler(epoch, lr):
        if epoch < 10:
            return lr
        else:
            return lr * ops.exp(-0.1)

    model = keras.models.Sequential([keras.layers.Dense(10)])
    model.compile(keras.optimizers.SGD(), loss='mse')
    round(model.optimizer.learning_rate, 5)
    0.01

    callback = keras.callbacks.LearningRateScheduler(scheduler)
    history = model.fit(np.arange(100).reshape(5, 20), np.zeros(5),
                        epochs=15, callbacks=[callback], verbose=0)
    round(model.optimizer.learning_rate, 5)
    0.00607

<br />

<br />

<br />

| ## Attributes ||
|---|---|
| `model` | <br /> <br /> |

<br />

## Methods

### `on_batch_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L102-L104)

    on_batch_begin(
        batch, logs=None
    )

A backwards compatibility alias for `on_train_batch_begin`.

### `on_batch_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L106-L108)

    on_batch_end(
        batch, logs=None
    )

A backwards compatibility alias for `on_train_batch_end`.

### `on_epoch_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/learning_rate_scheduler.py#L73-L90)

    on_epoch_begin(
        epoch, logs=None
    )

Called at the start of an epoch.

Subclasses should override for any actions to run. This function should
only be called during TRAIN mode.

<br />

<br />

<br />

| Args ||
|---|---|
| `epoch` | Integer, index of epoch. |
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_epoch_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/learning_rate_scheduler.py#L92-L102)

    on_epoch_end(
        epoch, logs=None
    )

Called at the end of an epoch.

Subclasses should override for any actions to run. This function should
only be called during TRAIN mode.

<br />

<br />

<br />

| Args ||
|---|---|
| `epoch` | Integer, index of epoch. |
| `logs` | Dict, metric results for this training epoch, and for the validation epoch if validation is performed. Validation result keys are prefixed with `val_`. For training epoch, the values of the `Model`'s metrics are returned. Example: `{'loss': 0.2, 'accuracy': 0.7}`. |

<br />

### `on_predict_batch_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L211-L225)

    on_predict_batch_begin(
        batch, logs=None
    )

Called at the beginning of a batch in `predict` methods.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_predict_batch_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L227-L240)

    on_predict_batch_end(
        batch, logs=None
    )

Called at the end of a batch in `predict` methods.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Aggregated metric results up until this batch. |

<br />

### `on_predict_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L288-L297)

    on_predict_begin(
        logs=None
    )

Called at the beginning of prediction.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_predict_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L299-L308)

    on_predict_end(
        logs=None
    )

Called at the end of prediction.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_test_batch_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L174-L191)

    on_test_batch_begin(
        batch, logs=None
    )

Called at the beginning of a batch in `evaluate` methods.

Also called at the beginning of a validation batch in the `fit`
methods, if validation data is provided.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_test_batch_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L193-L209)

    on_test_batch_end(
        batch, logs=None
    )

Called at the end of a batch in `evaluate` methods.

Also called at the end of a validation batch in the `fit`
methods, if validation data is provided.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Aggregated metric results up until this batch. |

<br />

### `on_test_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L265-L274)

    on_test_begin(
        logs=None
    )

Called at the beginning of evaluation or validation.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_test_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L276-L286)

    on_test_end(
        logs=None
    )

Called at the end of evaluation or validation.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently the output of the last call to `on_test_batch_end()` is passed to this argument for this method but that may change in the future. |

<br />

### `on_train_batch_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L139-L155)

    on_train_batch_begin(
        batch, logs=None
    )

Called at the beginning of a training batch in `fit` methods.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_train_batch_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L157-L172)

    on_train_batch_end(
        batch, logs=None
    )

Called at the end of a training batch in `fit` methods.

Subclasses should override for any actions to run.

Note that if the `steps_per_execution` argument to `compile` in
`Model` is set to `N`, this method will only be called every
`N` batches.

<br />

<br />

<br />

| Args ||
|---|---|
| `batch` | Integer, index of batch within the current epoch. |
| `logs` | Dict. Aggregated metric results up until this batch. |

<br />

### `on_train_begin`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L242-L251)

    on_train_begin(
        logs=None
    )

Called at the beginning of training.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently no data is passed to this argument for this method but that may change in the future. |

<br />

### `on_train_end`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L253-L263)

    on_train_end(
        logs=None
    )

Called at the end of training.

Subclasses should override for any actions to run.

<br />

<br />

<br />

| Args ||
|---|---|
| `logs` | Dict. Currently the output of the last call to `on_epoch_end()` is passed to this argument for this method but that may change in the future. |

<br />

### `set_model`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L74-L75)

    set_model(
        model
    )

### `set_params`

[View source](https://github.com/keras-team/keras/tree/v3.15.1/keras/src/callbacks/callback.py#L71-L72)

    set_params(
        params
    )