base.py — langchain Source File

Source Code

"""Base parser for language model outputs."""

from __future__ import annotations

import contextlib
from abc import ABC, abstractmethod
from typing import (
    TYPE_CHECKING,
    Any,
    Generic,
    TypeVar,
    cast,
)

from typing_extensions import override

from langchain_core.language_models import LanguageModelOutput
from langchain_core.messages import AnyMessage, BaseMessage
from langchain_core.outputs import ChatGeneration, Generation
from langchain_core.runnables import Runnable, RunnableConfig, RunnableSerializable
from langchain_core.runnables.config import run_in_executor

if TYPE_CHECKING:
    from langchain_core.prompt_values import PromptValue

T = TypeVar("T")
OutputParserLike = Runnable[LanguageModelOutput, T]


class BaseLLMOutputParser(ABC, Generic[T]):
    """Abstract base class for parsing the outputs of a model."""

    @abstractmethod
    def parse_result(self, result: list[Generation], *, partial: bool = False) -> T:
        """Parse a list of candidate model `Generation` objects into a specific format.

        Args:
            result: A list of `Generation` to be parsed.

                The `Generation` objects are assumed to be different candidate outputs
                for a single model input.
            partial: Whether to parse the output as a partial result.

                This is useful for parsers that can parse partial results.

        Returns:
            Structured output.
        """

    async def aparse_result(
        self, result: list[Generation], *, partial: bool = False
    ) -> T:
        """Parse a list of candidate model `Generation` objects into a specific format.

        Args:
            result: A list of `Generation` to be parsed.

                The Generations are assumed to be different candidate outputs for a
                single model input.
            partial: Whether to parse the output as a partial result.
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