aformat_messages() — langchain Function Reference

Source Code

libs/core/langchain_core/prompts/chat.py lines 1197–1223

    async def aformat_messages(self, **kwargs: Any) -> list[BaseMessage]:
        """Async format the chat template into a list of finalized messages.

        Args:
            **kwargs: Keyword arguments to use for filling in template variables
                in all the template messages in this chat template.

        Returns:
            List of formatted messages.

        Raises:
            ValueError: If unexpected input.
        """
        kwargs = self._merge_partial_and_user_variables(**kwargs)
        result = []
        for message_template in self.messages:
            if isinstance(message_template, BaseMessage):
                result.extend([message_template])
            elif isinstance(
                message_template, (BaseMessagePromptTemplate, BaseChatPromptTemplate)
            ):
                message = await message_template.aformat_messages(**kwargs)
                result.extend(message)
            else:
                msg = f"Unexpected input: {message_template}"
                raise ValueError(msg)  # noqa:TRY004
        return result