# tf.data.experimental.assert_cardinality

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| [![](https://www.tensorflow.org/images/GitHub-Mark-32px.png) View source on GitHub](https://github.com/tensorflow/tensorflow/blob/v2.14.0/tensorflow/python/data/experimental/ops/cardinality.py#L67-L96) |

Asserts the cardinality of the input dataset.

#### View aliases


**Compat aliases for migration**

See
[Migration guide](https://www.tensorflow.org/guide/migrate) for
more details.

[`tf.compat.v1.data.experimental.assert_cardinality`](https://www.tensorflow.org/api_docs/python/tf/data/experimental/assert_cardinality)

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    tf.data.experimental.assert_cardinality(
        expected_cardinality
    )

> [!NOTE]
> **Note:** The following assumes that "examples.tfrecord" contains 42 records.

    dataset = tf.data.TFRecordDataset("examples.tfrecord")
    cardinality = tf.data.experimental.cardinality(dataset)
    print((cardinality == tf.data.experimental.UNKNOWN_CARDINALITY).numpy())
    True
    dataset = dataset.apply(tf.data.experimental.assert_cardinality(42))
    print(tf.data.experimental.cardinality(dataset).numpy())
    42

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| ## Args ||
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| `expected_cardinality` | The expected cardinality of the input dataset. |

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| ## Returns ||
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| A `Dataset` transformation function, which can be passed to [`tf.data.Dataset.apply`](https://www.tensorflow.org/versions/r2.14/api_docs/python/tf/data/Dataset#apply). ||

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| ## Raises ||
|---|---|
| `FailedPreconditionError` | The assertion is checked at runtime (when iterating the dataset) and an error is raised if the actual and expected cardinality differ. |

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