"""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.
Parameters:
file: The file to write to.
color: The color to use for the text.
"""
[docs] def __init__(
self, filename: str, mode: str = "a", color: Optional[str] = None
) -> None:
"""Initialize callback handler.
Args:
filename: The filename to write to.
mode: The mode to open the file in. Defaults to "a".
color: The color to use for the text. Defaults to None.
"""
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.
Args:
serialized (Dict[str, Any]): The serialized chain.
inputs (Dict[str, Any]): The inputs to the chain.
**kwargs (Any): Additional keyword arguments.
"""
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.
Args:
outputs (Dict[str, Any]): The outputs of the chain.
**kwargs (Any): Additional keyword arguments.
"""
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.
Args:
action (AgentAction): The agent action.
color (Optional[str], optional): The color to use for the text.
Defaults to None.
**kwargs (Any): Additional keyword arguments.
"""
print_text(action.log, color=color or self.color, file=self.file)
[docs] def on_text(
self, text: str, color: Optional[str] = None, end: str = "", **kwargs: Any
) -> None:
"""Run when the agent ends.
Args:
text (str): The text to print.
color (Optional[str], optional): The color to use for the text.
Defaults to None.
end (str, optional): The end character. Defaults to "".
**kwargs (Any): Additional keyword arguments.
"""
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 the agent end.
Args:
finish (AgentFinish): The agent finish.
color (Optional[str], optional): The color to use for the text.
Defaults to None.
**kwargs (Any): Additional keyword arguments.
"""
print_text(finish.log, color=color or self.color, end="\n", file=self.file)