Source code for langchain_core.output_parsers.pydantic
import json
from typing import Generic, List, Type, TypeVar, Union
import pydantic # pydantic: ignore
from langchain_core.exceptions import OutputParserException
from langchain_core.output_parsers import JsonOutputParser
from langchain_core.outputs import Generation
from langchain_core.utils.pydantic import PYDANTIC_MAJOR_VERSION
if PYDANTIC_MAJOR_VERSION < 2:
PydanticBaseModel = pydantic.BaseModel
else:
from pydantic.v1 import BaseModel # pydantic: ignore
# Union type needs to be last assignment to PydanticBaseModel to make mypy happy.
PydanticBaseModel = Union[BaseModel, pydantic.BaseModel] # type: ignore
TBaseModel = TypeVar("TBaseModel", bound=PydanticBaseModel)
[docs]class PydanticOutputParser(JsonOutputParser, Generic[TBaseModel]):
"""使用pydantic模型解析输出。"""
pydantic_object: Type[TBaseModel] # type: ignore
"""要解析的pydantic模型。"""
def _parse_obj(self, obj: dict) -> TBaseModel:
if PYDANTIC_MAJOR_VERSION == 2:
try:
if issubclass(self.pydantic_object, pydantic.BaseModel):
return self.pydantic_object.model_validate(obj)
elif issubclass(self.pydantic_object, pydantic.v1.BaseModel):
return self.pydantic_object.parse_obj(obj)
else:
raise OutputParserException(
f"Unsupported model version for PydanticOutputParser: \
{self.pydantic_object.__class__}"
)
except (pydantic.ValidationError, pydantic.v1.ValidationError) as e:
raise self._parser_exception(e, obj)
else: # pydantic v1
try:
return self.pydantic_object.parse_obj(obj)
except pydantic.ValidationError as e:
raise self._parser_exception(e, obj)
def _parser_exception(
self, e: Exception, json_object: dict
) -> OutputParserException:
json_string = json.dumps(json_object)
name = self.pydantic_object.__name__
msg = f"Failed to parse {name} from completion {json_string}. Got: {e}"
return OutputParserException(msg, llm_output=json_string)
[docs] def parse_result(
self, result: List[Generation], *, partial: bool = False
) -> TBaseModel:
json_object = super().parse_result(result)
return self._parse_obj(json_object)
[docs] def parse(self, text: str) -> TBaseModel:
return super().parse(text)
@property
def _type(self) -> str:
return "pydantic"
@property
def OutputType(self) -> Type[TBaseModel]:
"""返回pydantic模型。"""
return self.pydantic_object
_PYDANTIC_FORMAT_INSTRUCTIONS = """The output should be formatted as a JSON instance that conforms to the JSON schema below.
As an example, for the schema {{"properties": {{"foo": {{"title": "Foo", "description": "a list of strings", "type": "array", "items": {{"type": "string"}}}}}}, "required": ["foo"]}}
the object {{"foo": ["bar", "baz"]}} is a well-formatted instance of the schema. The object {{"properties": {{"foo": ["bar", "baz"]}}}} is not well-formatted.
Here is the output schema:
```
{schema}
```""" # noqa: E501