prompt_values.py — langchain Source File

Source Code

"""**Prompt values** for language model prompts.

Prompt values are used to represent different pieces of prompts. They can be used to
represent text, images, or chat message pieces.
"""

from __future__ import annotations

from abc import ABC, abstractmethod
from collections.abc import Sequence
from typing import Literal, cast

from typing_extensions import TypedDict

from langchain_core.load.serializable import Serializable
from langchain_core.messages import (
    AnyMessage,
    BaseMessage,
    HumanMessage,
    get_buffer_string,
)


class PromptValue(Serializable, ABC):
    """Base abstract class for inputs to any language model.

    `PromptValues` can be converted to both LLM (pure text-generation) inputs and
    chat model inputs.
    """

    @classmethod
    def is_lc_serializable(cls) -> bool:
        """Return `True` as this class is serializable."""
        return True

    @classmethod
    def get_lc_namespace(cls) -> list[str]:
        """Get the namespace of the LangChain object.

        Returns:
            `["langchain", "schema", "prompt"]`
        """
        return ["langchain", "schema", "prompt"]

    @abstractmethod
    def to_string(self) -> str:
        """Return prompt value as string."""

    @abstractmethod
    def to_messages(self) -> list[BaseMessage]:
        """Return prompt as a list of messages."""


class StringPromptValue(PromptValue):
    """String prompt value."""

    text: str
    """Prompt text."""

    type: Literal["StringPromptValue"] = "StringPromptValue"
// ... (102 more lines)