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---

# Pydantic Dataclasses

Provide an enhanced dataclass that performs validation.

## dataclass

```python
def dataclass(
    *,
    init: Literal[False] = False,
    repr: bool = True,
    eq: bool = True,
    order: bool = False,
    unsafe_hash: bool = False,
    frozen: bool = False,
    config: ConfigDict | type[object] | None = None,
    validate_on_init: bool | None = None,
    kw_only: bool = ...,
    slots: bool = ...,
) -> Callable[[type[_T]], type[PydanticDataclass]]
def dataclass(
    _cls: type[_T],
    *,
    init: Literal[False] = False,
    repr: bool = True,
    eq: bool = True,
    order: bool = False,
    unsafe_hash: bool = False,
    frozen: bool | None = None,
    config: ConfigDict | type[object] | None = None,
    validate_on_init: bool | None = None,
    kw_only: bool = ...,
    slots: bool = ...,
) -> type[PydanticDataclass]
def dataclass(
    *,
    init: Literal[False] = False,
    repr: bool = True,
    eq: bool = True,
    order: bool = False,
    unsafe_hash: bool = False,
    frozen: bool | None = None,
    config: ConfigDict | type[object] | None = None,
    validate_on_init: bool | None = None,
) -> Callable[[type[_T]], type[PydanticDataclass]]
def dataclass(
    _cls: type[_T],
    *,
    init: Literal[False] = False,
    repr: bool = True,
    eq: bool = True,
    order: bool = False,
    unsafe_hash: bool = False,
    frozen: bool | None = None,
    config: ConfigDict | type[object] | None = None,
    validate_on_init: bool | None = None,
) -> type[PydanticDataclass]
```

Usage Documentation

[`dataclasses`](/docs/validation/latest/concepts/dataclasses)

A decorator used to create a Pydantic-enhanced dataclass, similar to the standard Python `dataclass`, but with added validation.

This function should be used similarly to `dataclasses.dataclass`.

### Returns

[`Callable`](https://docs.python.org/3/library/typing.html#typing.Callable)\[\[[`type`](https://docs.python.org/3/glossary.html#term-type)\[`_T`\]\], [`type`](https://docs.python.org/3/glossary.html#term-type)\[`PydanticDataclass`\]\] | [`type`](https://docs.python.org/3/glossary.html#term-type)\[`PydanticDataclass`\] -- A decorator that accepts a class as its argument and returns a Pydantic `dataclass`.

### Parameters

**`_cls`** : [`type`](https://docs.python.org/3/glossary.html#term-type)\[`_T`\] | [`None`](https://docs.python.org/3/library/constants.html#None) _Default:_ `None`

The target `dataclass`.

**`init`** : [`Literal`](https://docs.python.org/3/library/typing.html#typing.Literal)\[[`False`](https://docs.python.org/3/library/constants.html#False)\] _Default:_ `False`

Included for signature compatibility with `dataclasses.dataclass`, and is passed through to `dataclasses.dataclass` when appropriate. If specified, must be set to `False`, as pydantic inserts its own `__init__` function.

**`repr`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `True`

A boolean indicating whether to include the field in the `__repr__` output.

**`eq`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `True`

Determines if a `__eq__` method should be generated for the class.

**`order`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `False`

Determines if comparison magic methods should be generated, such as `__lt__`, but not `__eq__`.

**`unsafe_hash`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `False`

Determines if a `__hash__` method should be included in the class, as in `dataclasses.dataclass`.

**`frozen`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) | [`None`](https://docs.python.org/3/library/constants.html#None) _Default:_ `None`

Determines if the generated class should be a 'frozen' `dataclass`, which does not allow its attributes to be modified after it has been initialized. If not set, the value from the provided `config` argument will be used (and will default to `False` otherwise).

**`config`** : [`ConfigDict`](/docs/validation/latest/api/pydantic/config/#pydantic.config.ConfigDict) | [`type`](https://docs.python.org/3/glossary.html#term-type)\[[`object`](https://docs.python.org/3/glossary.html#term-object)\] | [`None`](https://docs.python.org/3/library/constants.html#None) _Default:_ `None`

The Pydantic config to use for the `dataclass`.

**`validate_on_init`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) | [`None`](https://docs.python.org/3/library/constants.html#None) _Default:_ `None`

A deprecated parameter included for backwards compatibility; in V2, all Pydantic dataclasses are validated on init.

**`kw_only`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `False`

Determines if `__init__` method parameters must be specified by keyword only. Defaults to `False`.

**`slots`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `False`

Determines if the generated class should be a 'slots' `dataclass`, which does not allow the addition of new attributes after instantiation.

### Raises

-   `AssertionError` -- Raised if `init` is not `False` or `validate_on_init` is `False`.

## rebuild\_dataclass

```python
def rebuild_dataclass(
    cls: type[PydanticDataclass],
    *,
    force: bool = False,
    raise_errors: bool = True,
    _parent_namespace_depth: int = 2,
    _types_namespace: MappingNamespace | None = None,
) -> bool | None
```

Try to rebuild the pydantic-core schema for the dataclass.

This may be necessary when one of the annotations is a ForwardRef which could not be resolved during the initial attempt to build the schema, and automatic rebuilding fails.

This is analogous to `BaseModel.model_rebuild`.

### Returns

[`bool`](https://docs.python.org/3/library/functions.html#bool) | [`None`](https://docs.python.org/3/library/constants.html#None) -- Returns `None` if the schema is already "complete" and rebuilding was not required. [`bool`](https://docs.python.org/3/library/functions.html#bool) | [`None`](https://docs.python.org/3/library/constants.html#None) -- If rebuilding _was_ required, returns `True` if rebuilding was successful, otherwise `False`.

### Parameters

**`cls`** : [`type`](https://docs.python.org/3/glossary.html#term-type)\[`PydanticDataclass`\]

The class to rebuild the pydantic-core schema for.

**`force`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `False`

Whether to force the rebuilding of the schema, defaults to `False`.

**`raise_errors`** : [`bool`](https://docs.python.org/3/library/functions.html#bool) _Default:_ `True`

Whether to raise errors, defaults to `True`.

**`_parent_namespace_depth`** : [`int`](https://docs.python.org/3/library/functions.html#int) _Default:_ `2`

The depth level of the parent namespace, defaults to 2.

**`_types_namespace`** : `MappingNamespace` | [`None`](https://docs.python.org/3/library/constants.html#None) _Default:_ `None`

The types namespace, defaults to `None`.

## is\_pydantic\_dataclass

```python
def is_pydantic_dataclass(class_: type[Any], /) -> TypeGuard[type[PydanticDataclass]]
```

Whether a class is a pydantic dataclass.

### Returns

[`TypeGuard`](https://docs.python.org/3/library/typing.html#typing.TypeGuard)\[[`type`](https://docs.python.org/3/glossary.html#term-type)\[`PydanticDataclass`\]\] -- `True` if the class is a pydantic dataclass, `False` otherwise.

### Parameters

**`class_`** : [`type`](https://docs.python.org/3/glossary.html#term-type)\[[`Any`](https://docs.python.org/3/library/typing.html#typing.Any)\]

The class.