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# `langchain.callbacks.streaming_stdout_final_only`.FinalStreamingStdOutCallbackHandler

class langchain.callbacks.streaming_stdout_final_only.FinalStreamingStdOutCallbackHandler(*, answer_prefix_tokens: Optional[List[str]] = None, strip_tokens: bool = True, stream_prefix: bool = False)

  Callback handler for streaming in agents. Only works with agents using LLMs that support streaming.

  Only the final output of the agent will be streamed.

  Instantiate FinalStreamingStdOutCallbackHandler.

  Parameters

    - answer_prefix_tokens (Optional[List[str]]) – Token sequence that prefixes the answer. Default is [“Final”, “Answer”, “:”]

    - strip_tokens (bool) – Ignore white spaces and new lines when comparing answer_prefix_tokens to last tokens? (to determine if answer has been reached)

    - stream_prefix (bool) – Should answer prefix itself also be streamed?

  Attributes

  `ignore_agent` | Whether to ignore agent callbacks.
  `ignore_chain` | Whether to ignore chain callbacks.
  `ignore_chat_model` | Whether to ignore chat model callbacks.
  `ignore_llm` | Whether to ignore LLM callbacks.
  `ignore_retriever` | Whether to ignore retriever callbacks.
  `ignore_retry` | Whether to ignore retry callbacks.
  `raise_error` |
  `run_inline` |

  Methods

  `__init__`(*[, answer_prefix_tokens, ...]) | Instantiate FinalStreamingStdOutCallbackHandler.
  `append_to_last_tokens`(token) |
  `check_if_answer_reached`() |
  `on_agent_action`(action, **kwargs) | Run on agent action.
  `on_agent_finish`(finish, **kwargs) | Run on agent end.
  `on_chain_end`(outputs, **kwargs) | Run when chain ends running.
  `on_chain_error`(error, **kwargs) | Run when chain errors.
  `on_chain_start`(serialized, inputs, **kwargs) | Run when chain starts running.
  `on_chat_model_start`(serialized, messages, ...) | Run when LLM starts running.
  `on_llm_end`(response, **kwargs) | Run when LLM ends running.
  `on_llm_error`(error, **kwargs) | Run when LLM errors.
  `on_llm_new_token`(token, **kwargs) | Run on new LLM token.
  `on_llm_start`(serialized, prompts, **kwargs) | Run when LLM starts running.
  `on_retriever_end`(documents, *, run_id[, ...]) | Run when Retriever ends running.
  `on_retriever_error`(error, *, run_id[, ...]) | Run when Retriever errors.
  `on_retriever_start`(serialized, query, *, run_id) | Run when Retriever starts running.
  `on_retry`(retry_state, *, run_id[, parent_run_id]) | Run on a retry event.
  `on_text`(text, **kwargs) | Run on arbitrary text.
  `on_tool_end`(output, **kwargs) | Run when tool ends running.
  `on_tool_error`(error, **kwargs) | Run when tool errors.
  `on_tool_start`(serialized, input_str, **kwargs) | Run when tool starts running.

  __init__(*, answer_prefix_tokens: Optional[List[str]] = None, strip_tokens: bool = True, stream_prefix: bool = False) → None

    Instantiate FinalStreamingStdOutCallbackHandler.

    Parameters

      - answer_prefix_tokens (Optional[List[str]]) – Token sequence that prefixes the answer. Default is [“Final”, “Answer”, “:”]

      - strip_tokens (bool) – Ignore white spaces and new lines when comparing answer_prefix_tokens to last tokens? (to determine if answer has been reached)

      - stream_prefix (bool) – Should answer prefix itself also be streamed?

    Return type

      None

  append_to_last_tokens(token: str) → None
    Parameters

      token (str) –

    Return type

      None

  check_if_answer_reached() → bool
    Return type

      bool

  on_agent_action(action: AgentAction, **kwargs: Any) → Any

    Run on agent action.

    Parameters

      - action (AgentAction) –

      - kwargs (Any) –

    Return type

      Any

  on_agent_finish(finish: AgentFinish, **kwargs: Any) → None

    Run on agent end.

    Parameters

      - finish (AgentFinish) –

      - kwargs (Any) –

    Return type

      None

  on_chain_end(outputs: Dict[str, Any], **kwargs: Any) → None

    Run when chain ends running.

    Parameters

      - outputs (Dict[str, Any]) –

      - kwargs (Any) –

    Return type

      None

  on_chain_error(error: BaseException, **kwargs: Any) → None

    Run when chain errors.

    Parameters

      - error (BaseException) –

      - kwargs (Any) –

    Return type

      None

  on_chain_start(serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any) → None

    Run when chain starts running.

    Parameters

      - serialized (Dict[str, Any]) –

      - inputs (Dict[str, Any]) –

      - kwargs (Any) –

    Return type

      None

  on_chat_model_start(serialized: Dict[str, Any], messages: List[List[BaseMessage]], **kwargs: Any) → None

    Run when LLM starts running.

    Parameters

      - serialized (Dict[str, Any]) –

      - messages (List[List[BaseMessage]]) –

      - kwargs (Any) –

    Return type

      None

  on_llm_end(response: LLMResult, **kwargs: Any) → None

    Run when LLM ends running.

    Parameters

      - response (LLMResult) –

      - kwargs (Any) –

    Return type

      None

  on_llm_error(error: BaseException, **kwargs: Any) → None

    Run when LLM errors.

    Parameters

      - error (BaseException) –

      - kwargs (Any) –

    Return type

      None

  on_llm_new_token(token: str, **kwargs: Any) → None

    Run on new LLM token. Only available when streaming is enabled.

    Parameters

      - token (str) –

      - kwargs (Any) –

    Return type

      None

  on_llm_start(serialized: Dict[str, Any], prompts: List[str], **kwargs: Any) → None

    Run when LLM starts running.

    Parameters

      - serialized (Dict[str, Any]) –

      - prompts (List[str]) –

      - kwargs (Any) –

    Return type

      None

  on_retriever_end(documents: Sequence[Document], *, run_id: UUID, parent_run_id: Optional[UUID] = None, **kwargs: Any) → Any

    Run when Retriever ends running.

    Parameters

      - documents (Sequence[Document]) –

      - run_id (UUID) –

      - parent_run_id (Optional[UUID]) –

      - kwargs (Any) –

    Return type

      Any

  on_retriever_error(error: BaseException, *, run_id: UUID, parent_run_id: Optional[UUID] = None, **kwargs: Any) → Any

    Run when Retriever errors.

    Parameters

      - error (BaseException) –

      - run_id (UUID) –

      - parent_run_id (Optional[UUID]) –

      - kwargs (Any) –

    Return type

      Any

  on_retriever_start(serialized: Dict[str, Any], query: str, *, run_id: UUID, parent_run_id: Optional[UUID] = None, tags: Optional[List[str]] = None, metadata: Optional[Dict[str, Any]] = None, **kwargs: Any) → Any

    Run when Retriever starts running.

    Parameters

      - serialized (Dict[str, Any]) –

      - query (str) –

      - run_id (UUID) –

      - parent_run_id (Optional[UUID]) –

      - tags (Optional[List[str]]) –

      - metadata (Optional[Dict[str, Any]]) –

      - kwargs (Any) –

    Return type

      Any

  on_retry(retry_state: RetryCallState, *, run_id: UUID, parent_run_id: Optional[UUID] = None, **kwargs: Any) → Any

    Run on a retry event.

    Parameters

      - retry_state (RetryCallState) –

      - run_id (UUID) –

      - parent_run_id (Optional[UUID]) –

      - kwargs (Any) –

    Return type

      Any

  on_text(text: str, **kwargs: Any) → None

    Run on arbitrary text.

    Parameters

      - text (str) –

      - kwargs (Any) –

    Return type

      None

  on_tool_end(output: Any, **kwargs: Any) → None

    Run when tool ends running.

    Parameters

      - output (Any) –

      - kwargs (Any) –

    Return type

      None

  on_tool_error(error: BaseException, **kwargs: Any) → None

    Run when tool errors.

    Parameters

      - error (BaseException) –

      - kwargs (Any) –

    Return type

      None

  on_tool_start(serialized: Dict[str, Any], input_str: str, **kwargs: Any) → None

    Run when tool starts running.

    Parameters

      - serialized (Dict[str, Any]) –

      - input_str (str) –

      - kwargs (Any) –

    Return type

      None