langchain.callbacks.file.FileCallbackHandler

class langchain.callbacks.file.FileCallbackHandler(filename: str, mode: str = 'a', color: Optional[str] = None)

Callback Handler that writes to a file.

Initialize callback handler.

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__(filename[, mode, color])	Initialize callback handler.
on_agent_action(action[, color])	Run on agent action.
on_agent_finish(finish[, color])	Run on agent end.
on_chain_end(outputs, **kwargs)	Print out that we finished a chain.
on_chain_error(error, *, run_id[, parent_run_id])	Run when chain errors.
on_chain_start(serialized, inputs, **kwargs)	Print out that we are entering a chain.
on_chat_model_start(serialized, messages, *, ...)	Run when a chat model starts running.
on_llm_end(response, *, run_id[, parent_run_id])	Run when LLM ends running.
on_llm_error(error, *, run_id[, parent_run_id])	Run when LLM errors. :param error: The error that occurred. :type error: BaseException :param kwargs: Additional keyword arguments. - response (LLMResult): The response which was generated before the error occurred. :type kwargs: Any.
on_llm_new_token(token, *[, chunk, ...])	Run on new LLM token.
on_llm_start(serialized, prompts, *, run_id)	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[, color, end])	Run when agent ends.
on_tool_end(output[, color, ...])	If not the final action, print out observation.
on_tool_error(error, *, run_id[, parent_run_id])	Run when tool errors.
on_tool_start(serialized, input_str, *, run_id)	Run when tool starts running.

__init__(filename: str, mode: str = 'a', color: Optional[str] = None) → None

Initialize callback handler.

on_agent_action(action: AgentAction, color: Optional[str] = None, **kwargs: Any) → Any

Run on agent action.

on_agent_finish(finish: AgentFinish, color: Optional[str] = None, **kwargs: Any) → None

Run on agent end.

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

Print out that we finished a chain.

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

Run when chain errors.

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

Print out that we are entering a chain.

on_chat_model_start(serialized: Dict[str, Any], messages: List[List[BaseMessage]], *, 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 a chat model starts running.

on_llm_end(response: LLMResult, *, run_id: UUID, parent_run_id: Optional[UUID] = None, **kwargs: Any) → Any

Run when LLM ends running.

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

Run when LLM errors. :param error: The error that occurred. :type error: BaseException :param kwargs: Additional keyword arguments.

• response (LLMResult): The response which was generated before

  the error occurred.

on_llm_new_token(token: str, *, chunk: Optional[Union[GenerationChunk, ChatGenerationChunk]] = None, run_id: UUID, parent_run_id: Optional[UUID] = None, **kwargs: Any) → Any

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

Parameters

• token (str) – The new token.

• chunk (GenerationChunk | ChatGenerationChunk) – The new generated chunk,

• information. (containing content and other) –

on_llm_start(serialized: Dict[str, Any], prompts: List[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 LLM starts running.

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

Run when Retriever ends running.

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

Run when Retriever errors.

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.

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

Run on a retry event.

on_text(text: str, color: Optional[str] = None, end: str = '', **kwargs: Any) → None

Run when agent ends.

on_tool_end(output: str, color: Optional[str] = None, observation_prefix: Optional[str] = None, llm_prefix: Optional[str] = None, **kwargs: Any) → None

If not the final action, print out observation.

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

Run when tool errors.

on_tool_start(serialized: Dict[str, Any], input_str: 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 tool starts running.

Examples using FileCallbackHandler

• Logging to file