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

Examples using FinalStreamingStdOutCallbackHandler

• Streaming final agent output