Method assign

libs/core/langchain_core/runnables/base.py:533–576

Assigns new fields to the dict output of this runnable. Returns a new runnable. .. code-block:: python from langchain_community.llms.fake import FakeStreamingListLLM from langchain_core.output_parsers import StrOutputParser from langchain_core.pr

(
        self,
        **kwargs: Union[
            Runnable[Dict[str, Any], Any],
            Callable[[Dict[str, Any]], Any],
            Mapping[
                str,
                Union[Runnable[Dict[str, Any], Any], Callable[[Dict[str, Any]], Any]],
            ],
        ],
    )

        return self | RunnablePick(keys)

    def assign(
        self,
        **kwargs: Union[
            Runnable[Dict[str, Any], Any],
            Callable[[Dict[str, Any]], Any],
            Mapping[
                str,
                Union[Runnable[Dict[str, Any], Any], Callable[[Dict[str, Any]], Any]],
            ],
        ],
    ) -> RunnableSerializable[Any, Any]:
        """Assigns new fields to the dict output of this runnable.
        Returns a new runnable.

        .. code-block:: python

            from langchain_community.llms.fake import FakeStreamingListLLM
            from langchain_core.output_parsers import StrOutputParser
            from langchain_core.prompts import SystemMessagePromptTemplate
            from langchain_core.runnables import Runnable
            from operator import itemgetter

            prompt = (
                SystemMessagePromptTemplate.from_template("You are a nice assistant.")
                + "{question}"
            )
            llm = FakeStreamingListLLM(responses=["foo-lish"])

            chain: Runnable = prompt | llm | {"str": StrOutputParser()}

            chain_with_assign = chain.assign(hello=itemgetter("str") | llm)

            print(chain_with_assign.input_schema.schema())
            # {'title': 'PromptInput', 'type': 'object', 'properties':
            {'question': {'title': 'Question', 'type': 'string'}}}
            print(chain_with_assign.output_schema.schema()) #
            {'title': 'RunnableSequenceOutput', 'type': 'object', 'properties':
            {'str': {'title': 'Str',
            'type': 'string'}, 'hello': {'title': 'Hello', 'type': 'string'}}}

        """
        from langchain_core.runnables.passthrough import RunnableAssign

        return self | RunnableAssign(RunnableParallel(kwargs))

    """ --- Public API --- """