---
title: LambdaCallback
description: Create a simple callback on the fly using lambda functions.
canonical: >-
  https://lightning.ai/docs/pytorch/stable/optional-api/api/lightning.pytorch.callbacks.LambdaCallback
---
# LambdaCallback {#lambdacallback}

### `class lightning.pytorch.callbacks.LambdaCallback(setup=None, teardown=None, on_fit_start=None, on_fit_end=None, on_sanity_check_start=None, on_sanity_check_end=None, on_train_batch_start=None, on_train_batch_end=None, on_train_epoch_start=None, on_train_epoch_end=None, on_validation_epoch_start=None, on_validation_epoch_end=None, on_test_epoch_start=None, on_test_epoch_end=None, on_validation_batch_start=None, on_validation_batch_end=None, on_test_batch_start=None, on_test_batch_end=None, on_train_start=None, on_train_end=None, on_validation_start=None, on_validation_end=None, on_test_start=None, on_test_end=None, on_exception=None, on_save_checkpoint=None, on_load_checkpoint=None, on_before_backward=None, on_after_backward=None, on_before_optimizer_step=None, on_before_zero_grad=None, on_predict_start=None, on_predict_end=None, on_predict_batch_start=None, on_predict_batch_end=None, on_predict_epoch_start=None, on_predict_epoch_end=None)` {#lightning.pytorch.callbacks.LambdaCallback}

Bases: [`Callback`](/docs/pytorch/2.6.6/optional-api/api/lightning.pytorch.callbacks.Callback.md#lightning.pytorch.callbacks.Callback "lightning.pytorch.callbacks.callback.Callback")

Create a simple callback on the fly using lambda functions.

Parameters:

**\*\*kwargs** – hooks supported by [`Callback`](/docs/pytorch/2.6.6/optional-api/api/lightning.pytorch.callbacks.Callback.md#lightning.pytorch.callbacks.Callback "lightning.pytorch.callbacks.callback.Callback")

Example:

```python
>>> from lightning.pytorch import Trainer
>>> from lightning.pytorch.callbacks import LambdaCallback
>>> trainer = Trainer(callbacks=[LambdaCallback(setup=lambda *args: print('setup'))])
```

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- Parent: [Api](/docs/pytorch/2.6.6/optional-api/api.md)