Source code for langchain_core.callbacks.file

"""Callback Handler that writes to a file."""

from __future__ import annotations

from typing import Any, Dict, Optional, TextIO, cast

from langchain_core.agents import AgentAction, AgentFinish
from langchain_core.callbacks import BaseCallbackHandler
from langchain_core.utils.input import print_text


[docs]class FileCallbackHandler(BaseCallbackHandler): """Callback Handler that writes to a file."""
[docs] def __init__( self, filename: str, mode: str = "a", color: Optional[str] = None ) -> None: """Initialize callback handler.""" self.file = cast(TextIO, open(filename, mode, encoding="utf-8")) self.color = color
def __del__(self) -> None: """Destructor to cleanup when done.""" self.file.close()
[docs] def on_chain_start( self, serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any ) -> None: """Print out that we are entering a chain.""" class_name = serialized.get("name", serialized.get("id", ["<unknown>"])[-1]) print_text( f"\n\n\033[1m> Entering new {class_name} chain...\033[0m", end="\n", file=self.file, )
[docs] def on_chain_end(self, outputs: Dict[str, Any], **kwargs: Any) -> None: """Print out that we finished a chain.""" print_text("\n\033[1m> Finished chain.\033[0m", end="\n", file=self.file)
[docs] def on_agent_action( self, action: AgentAction, color: Optional[str] = None, **kwargs: Any ) -> Any: """Run on agent action.""" print_text(action.log, color=color or self.color, file=self.file)
[docs] def on_tool_end( self, 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.""" if observation_prefix is not None: print_text(f"\n{observation_prefix}", file=self.file) print_text(output, color=color or self.color, file=self.file) if llm_prefix is not None: print_text(f"\n{llm_prefix}", file=self.file)
[docs] def on_text( self, text: str, color: Optional[str] = None, end: str = "", **kwargs: Any ) -> None: """Run when agent ends.""" print_text(text, color=color or self.color, end=end, file=self.file)
[docs] def on_agent_finish( self, finish: AgentFinish, color: Optional[str] = None, **kwargs: Any ) -> None: """Run on agent end.""" print_text(finish.log, color=color or self.color, end="\n", file=self.file)