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  1. """This module contains related classes and functions for serialization."""
  2. from __future__ import annotations
  3. import dataclasses
  4. from functools import partial, partialmethod
  5. from typing import TYPE_CHECKING, Annotated, Any, Callable, Literal, TypeVar, overload
  6. from pydantic_core import PydanticUndefined, core_schema
  7. from pydantic_core.core_schema import SerializationInfo, SerializerFunctionWrapHandler, WhenUsed
  8. from typing_extensions import TypeAlias
  9. from . import PydanticUndefinedAnnotation
  10. from ._internal import _decorators, _internal_dataclass
  11. from .annotated_handlers import GetCoreSchemaHandler
  12. @dataclasses.dataclass(**_internal_dataclass.slots_true, frozen=True)
  13. class PlainSerializer:
  14. """Plain serializers use a function to modify the output of serialization.
  15. This is particularly helpful when you want to customize the serialization for annotated types.
  16. Consider an input of `list`, which will be serialized into a space-delimited string.
  17. ```python
  18. from typing import Annotated
  19. from pydantic import BaseModel, PlainSerializer
  20. CustomStr = Annotated[
  21. list, PlainSerializer(lambda x: ' '.join(x), return_type=str)
  22. ]
  23. class StudentModel(BaseModel):
  24. courses: CustomStr
  25. student = StudentModel(courses=['Math', 'Chemistry', 'English'])
  26. print(student.model_dump())
  27. #> {'courses': 'Math Chemistry English'}
  28. ```
  29. Attributes:
  30. func: The serializer function.
  31. return_type: The return type for the function. If omitted it will be inferred from the type annotation.
  32. when_used: Determines when this serializer should be used. Accepts a string with values `'always'`,
  33. `'unless-none'`, `'json'`, and `'json-unless-none'`. Defaults to 'always'.
  34. """
  35. func: core_schema.SerializerFunction
  36. return_type: Any = PydanticUndefined
  37. when_used: WhenUsed = 'always'
  38. def __get_pydantic_core_schema__(self, source_type: Any, handler: GetCoreSchemaHandler) -> core_schema.CoreSchema:
  39. """Gets the Pydantic core schema.
  40. Args:
  41. source_type: The source type.
  42. handler: The `GetCoreSchemaHandler` instance.
  43. Returns:
  44. The Pydantic core schema.
  45. """
  46. schema = handler(source_type)
  47. if self.return_type is not PydanticUndefined:
  48. return_type = self.return_type
  49. else:
  50. try:
  51. # Do not pass in globals as the function could be defined in a different module.
  52. # Instead, let `get_callable_return_type` infer the globals to use, but still pass
  53. # in locals that may contain a parent/rebuild namespace:
  54. return_type = _decorators.get_callable_return_type(
  55. self.func,
  56. localns=handler._get_types_namespace().locals,
  57. )
  58. except NameError as e:
  59. raise PydanticUndefinedAnnotation.from_name_error(e) from e
  60. return_schema = None if return_type is PydanticUndefined else handler.generate_schema(return_type)
  61. schema['serialization'] = core_schema.plain_serializer_function_ser_schema(
  62. function=self.func,
  63. info_arg=_decorators.inspect_annotated_serializer(self.func, 'plain'),
  64. return_schema=return_schema,
  65. when_used=self.when_used,
  66. )
  67. return schema
  68. @dataclasses.dataclass(**_internal_dataclass.slots_true, frozen=True)
  69. class WrapSerializer:
  70. """Wrap serializers receive the raw inputs along with a handler function that applies the standard serialization
  71. logic, and can modify the resulting value before returning it as the final output of serialization.
  72. For example, here's a scenario in which a wrap serializer transforms timezones to UTC **and** utilizes the existing `datetime` serialization logic.
  73. ```python
  74. from datetime import datetime, timezone
  75. from typing import Annotated, Any
  76. from pydantic import BaseModel, WrapSerializer
  77. class EventDatetime(BaseModel):
  78. start: datetime
  79. end: datetime
  80. def convert_to_utc(value: Any, handler, info) -> dict[str, datetime]:
  81. # Note that `handler` can actually help serialize the `value` for
  82. # further custom serialization in case it's a subclass.
  83. partial_result = handler(value, info)
  84. if info.mode == 'json':
  85. return {
  86. k: datetime.fromisoformat(v).astimezone(timezone.utc)
  87. for k, v in partial_result.items()
  88. }
  89. return {k: v.astimezone(timezone.utc) for k, v in partial_result.items()}
  90. UTCEventDatetime = Annotated[EventDatetime, WrapSerializer(convert_to_utc)]
  91. class EventModel(BaseModel):
  92. event_datetime: UTCEventDatetime
  93. dt = EventDatetime(
  94. start='2024-01-01T07:00:00-08:00', end='2024-01-03T20:00:00+06:00'
  95. )
  96. event = EventModel(event_datetime=dt)
  97. print(event.model_dump())
  98. '''
  99. {
  100. 'event_datetime': {
  101. 'start': datetime.datetime(
  102. 2024, 1, 1, 15, 0, tzinfo=datetime.timezone.utc
  103. ),
  104. 'end': datetime.datetime(
  105. 2024, 1, 3, 14, 0, tzinfo=datetime.timezone.utc
  106. ),
  107. }
  108. }
  109. '''
  110. print(event.model_dump_json())
  111. '''
  112. {"event_datetime":{"start":"2024-01-01T15:00:00Z","end":"2024-01-03T14:00:00Z"}}
  113. '''
  114. ```
  115. Attributes:
  116. func: The serializer function to be wrapped.
  117. return_type: The return type for the function. If omitted it will be inferred from the type annotation.
  118. when_used: Determines when this serializer should be used. Accepts a string with values `'always'`,
  119. `'unless-none'`, `'json'`, and `'json-unless-none'`. Defaults to 'always'.
  120. """
  121. func: core_schema.WrapSerializerFunction
  122. return_type: Any = PydanticUndefined
  123. when_used: WhenUsed = 'always'
  124. def __get_pydantic_core_schema__(self, source_type: Any, handler: GetCoreSchemaHandler) -> core_schema.CoreSchema:
  125. """This method is used to get the Pydantic core schema of the class.
  126. Args:
  127. source_type: Source type.
  128. handler: Core schema handler.
  129. Returns:
  130. The generated core schema of the class.
  131. """
  132. schema = handler(source_type)
  133. if self.return_type is not PydanticUndefined:
  134. return_type = self.return_type
  135. else:
  136. try:
  137. # Do not pass in globals as the function could be defined in a different module.
  138. # Instead, let `get_callable_return_type` infer the globals to use, but still pass
  139. # in locals that may contain a parent/rebuild namespace:
  140. return_type = _decorators.get_callable_return_type(
  141. self.func,
  142. localns=handler._get_types_namespace().locals,
  143. )
  144. except NameError as e:
  145. raise PydanticUndefinedAnnotation.from_name_error(e) from e
  146. return_schema = None if return_type is PydanticUndefined else handler.generate_schema(return_type)
  147. schema['serialization'] = core_schema.wrap_serializer_function_ser_schema(
  148. function=self.func,
  149. info_arg=_decorators.inspect_annotated_serializer(self.func, 'wrap'),
  150. return_schema=return_schema,
  151. when_used=self.when_used,
  152. )
  153. return schema
  154. if TYPE_CHECKING:
  155. _Partial: TypeAlias = 'partial[Any] | partialmethod[Any]'
  156. FieldPlainSerializer: TypeAlias = 'core_schema.SerializerFunction | _Partial'
  157. """A field serializer method or function in `plain` mode."""
  158. FieldWrapSerializer: TypeAlias = 'core_schema.WrapSerializerFunction | _Partial'
  159. """A field serializer method or function in `wrap` mode."""
  160. FieldSerializer: TypeAlias = 'FieldPlainSerializer | FieldWrapSerializer'
  161. """A field serializer method or function."""
  162. _FieldPlainSerializerT = TypeVar('_FieldPlainSerializerT', bound=FieldPlainSerializer)
  163. _FieldWrapSerializerT = TypeVar('_FieldWrapSerializerT', bound=FieldWrapSerializer)
  164. @overload
  165. def field_serializer(
  166. field: str,
  167. /,
  168. *fields: str,
  169. mode: Literal['wrap'],
  170. return_type: Any = ...,
  171. when_used: WhenUsed = ...,
  172. check_fields: bool | None = ...,
  173. ) -> Callable[[_FieldWrapSerializerT], _FieldWrapSerializerT]: ...
  174. @overload
  175. def field_serializer(
  176. field: str,
  177. /,
  178. *fields: str,
  179. mode: Literal['plain'] = ...,
  180. return_type: Any = ...,
  181. when_used: WhenUsed = ...,
  182. check_fields: bool | None = ...,
  183. ) -> Callable[[_FieldPlainSerializerT], _FieldPlainSerializerT]: ...
  184. def field_serializer(
  185. *fields: str,
  186. mode: Literal['plain', 'wrap'] = 'plain',
  187. return_type: Any = PydanticUndefined,
  188. when_used: WhenUsed = 'always',
  189. check_fields: bool | None = None,
  190. ) -> (
  191. Callable[[_FieldWrapSerializerT], _FieldWrapSerializerT]
  192. | Callable[[_FieldPlainSerializerT], _FieldPlainSerializerT]
  193. ):
  194. """Decorator that enables custom field serialization.
  195. In the below example, a field of type `set` is used to mitigate duplication. A `field_serializer` is used to serialize the data as a sorted list.
  196. ```python
  197. from typing import Set
  198. from pydantic import BaseModel, field_serializer
  199. class StudentModel(BaseModel):
  200. name: str = 'Jane'
  201. courses: Set[str]
  202. @field_serializer('courses', when_used='json')
  203. def serialize_courses_in_order(self, courses: Set[str]):
  204. return sorted(courses)
  205. student = StudentModel(courses={'Math', 'Chemistry', 'English'})
  206. print(student.model_dump_json())
  207. #> {"name":"Jane","courses":["Chemistry","English","Math"]}
  208. ```
  209. See [Custom serializers](../concepts/serialization.md#custom-serializers) for more information.
  210. Four signatures are supported:
  211. - `(self, value: Any, info: FieldSerializationInfo)`
  212. - `(self, value: Any, nxt: SerializerFunctionWrapHandler, info: FieldSerializationInfo)`
  213. - `(value: Any, info: SerializationInfo)`
  214. - `(value: Any, nxt: SerializerFunctionWrapHandler, info: SerializationInfo)`
  215. Args:
  216. fields: Which field(s) the method should be called on.
  217. mode: The serialization mode.
  218. - `plain` means the function will be called instead of the default serialization logic,
  219. - `wrap` means the function will be called with an argument to optionally call the
  220. default serialization logic.
  221. return_type: Optional return type for the function, if omitted it will be inferred from the type annotation.
  222. when_used: Determines the serializer will be used for serialization.
  223. check_fields: Whether to check that the fields actually exist on the model.
  224. Returns:
  225. The decorator function.
  226. """
  227. def dec(f: FieldSerializer) -> _decorators.PydanticDescriptorProxy[Any]:
  228. dec_info = _decorators.FieldSerializerDecoratorInfo(
  229. fields=fields,
  230. mode=mode,
  231. return_type=return_type,
  232. when_used=when_used,
  233. check_fields=check_fields,
  234. )
  235. return _decorators.PydanticDescriptorProxy(f, dec_info) # pyright: ignore[reportArgumentType]
  236. return dec # pyright: ignore[reportReturnType]
  237. if TYPE_CHECKING:
  238. # The first argument in the following callables represent the `self` type:
  239. ModelPlainSerializerWithInfo: TypeAlias = Callable[[Any, SerializationInfo], Any]
  240. """A model serializer method with the `info` argument, in `plain` mode."""
  241. ModelPlainSerializerWithoutInfo: TypeAlias = Callable[[Any], Any]
  242. """A model serializer method without the `info` argument, in `plain` mode."""
  243. ModelPlainSerializer: TypeAlias = 'ModelPlainSerializerWithInfo | ModelPlainSerializerWithoutInfo'
  244. """A model serializer method in `plain` mode."""
  245. ModelWrapSerializerWithInfo: TypeAlias = Callable[[Any, SerializerFunctionWrapHandler, SerializationInfo], Any]
  246. """A model serializer method with the `info` argument, in `wrap` mode."""
  247. ModelWrapSerializerWithoutInfo: TypeAlias = Callable[[Any, SerializerFunctionWrapHandler], Any]
  248. """A model serializer method without the `info` argument, in `wrap` mode."""
  249. ModelWrapSerializer: TypeAlias = 'ModelWrapSerializerWithInfo | ModelWrapSerializerWithoutInfo'
  250. """A model serializer method in `wrap` mode."""
  251. ModelSerializer: TypeAlias = 'ModelPlainSerializer | ModelWrapSerializer'
  252. _ModelPlainSerializerT = TypeVar('_ModelPlainSerializerT', bound=ModelPlainSerializer)
  253. _ModelWrapSerializerT = TypeVar('_ModelWrapSerializerT', bound=ModelWrapSerializer)
  254. @overload
  255. def model_serializer(f: _ModelPlainSerializerT, /) -> _ModelPlainSerializerT: ...
  256. @overload
  257. def model_serializer(
  258. *, mode: Literal['wrap'], when_used: WhenUsed = 'always', return_type: Any = ...
  259. ) -> Callable[[_ModelWrapSerializerT], _ModelWrapSerializerT]: ...
  260. @overload
  261. def model_serializer(
  262. *,
  263. mode: Literal['plain'] = ...,
  264. when_used: WhenUsed = 'always',
  265. return_type: Any = ...,
  266. ) -> Callable[[_ModelPlainSerializerT], _ModelPlainSerializerT]: ...
  267. def model_serializer(
  268. f: _ModelPlainSerializerT | _ModelWrapSerializerT | None = None,
  269. /,
  270. *,
  271. mode: Literal['plain', 'wrap'] = 'plain',
  272. when_used: WhenUsed = 'always',
  273. return_type: Any = PydanticUndefined,
  274. ) -> (
  275. _ModelPlainSerializerT
  276. | Callable[[_ModelWrapSerializerT], _ModelWrapSerializerT]
  277. | Callable[[_ModelPlainSerializerT], _ModelPlainSerializerT]
  278. ):
  279. """Decorator that enables custom model serialization.
  280. This is useful when a model need to be serialized in a customized manner, allowing for flexibility beyond just specific fields.
  281. An example would be to serialize temperature to the same temperature scale, such as degrees Celsius.
  282. ```python
  283. from typing import Literal
  284. from pydantic import BaseModel, model_serializer
  285. class TemperatureModel(BaseModel):
  286. unit: Literal['C', 'F']
  287. value: int
  288. @model_serializer()
  289. def serialize_model(self):
  290. if self.unit == 'F':
  291. return {'unit': 'C', 'value': int((self.value - 32) / 1.8)}
  292. return {'unit': self.unit, 'value': self.value}
  293. temperature = TemperatureModel(unit='F', value=212)
  294. print(temperature.model_dump())
  295. #> {'unit': 'C', 'value': 100}
  296. ```
  297. Two signatures are supported for `mode='plain'`, which is the default:
  298. - `(self)`
  299. - `(self, info: SerializationInfo)`
  300. And two other signatures for `mode='wrap'`:
  301. - `(self, nxt: SerializerFunctionWrapHandler)`
  302. - `(self, nxt: SerializerFunctionWrapHandler, info: SerializationInfo)`
  303. See [Custom serializers](../concepts/serialization.md#custom-serializers) for more information.
  304. Args:
  305. f: The function to be decorated.
  306. mode: The serialization mode.
  307. - `'plain'` means the function will be called instead of the default serialization logic
  308. - `'wrap'` means the function will be called with an argument to optionally call the default
  309. serialization logic.
  310. when_used: Determines when this serializer should be used.
  311. return_type: The return type for the function. If omitted it will be inferred from the type annotation.
  312. Returns:
  313. The decorator function.
  314. """
  315. def dec(f: ModelSerializer) -> _decorators.PydanticDescriptorProxy[Any]:
  316. dec_info = _decorators.ModelSerializerDecoratorInfo(mode=mode, return_type=return_type, when_used=when_used)
  317. return _decorators.PydanticDescriptorProxy(f, dec_info)
  318. if f is None:
  319. return dec # pyright: ignore[reportReturnType]
  320. else:
  321. return dec(f) # pyright: ignore[reportReturnType]
  322. AnyType = TypeVar('AnyType')
  323. if TYPE_CHECKING:
  324. SerializeAsAny = Annotated[AnyType, ...] # SerializeAsAny[list[str]] will be treated by type checkers as list[str]
  325. """Force serialization to ignore whatever is defined in the schema and instead ask the object
  326. itself how it should be serialized.
  327. In particular, this means that when model subclasses are serialized, fields present in the subclass
  328. but not in the original schema will be included.
  329. """
  330. else:
  331. @dataclasses.dataclass(**_internal_dataclass.slots_true)
  332. class SerializeAsAny: # noqa: D101
  333. def __class_getitem__(cls, item: Any) -> Any:
  334. return Annotated[item, SerializeAsAny()]
  335. def __get_pydantic_core_schema__(
  336. self, source_type: Any, handler: GetCoreSchemaHandler
  337. ) -> core_schema.CoreSchema:
  338. schema = handler(source_type)
  339. schema_to_update = schema
  340. while schema_to_update['type'] == 'definitions':
  341. schema_to_update = schema_to_update.copy()
  342. schema_to_update = schema_to_update['schema']
  343. schema_to_update['serialization'] = core_schema.wrap_serializer_function_ser_schema(
  344. lambda x, h: h(x), schema=core_schema.any_schema()
  345. )
  346. return schema
  347. __hash__ = object.__hash__