Source code for langchain_core.callbacks.stdout

"""Callback Handler that prints to std out."""

from __future__ import annotations

from typing import TYPE_CHECKING, Any, Dict, Optional

from langchain_core.callbacks.base import BaseCallbackHandler
from langchain_core.utils import print_text

    from langchain_core.agents import AgentAction, AgentFinish

[docs]class StdOutCallbackHandler(BaseCallbackHandler): """Callback Handler that prints to std out."""
[docs] def __init__(self, color: Optional[str] = None) -> None: """Initialize callback handler.""" self.color = color
[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(f"\n\n\033[1m> Entering new {class_name} chain...\033[0m") # noqa: T201
[docs] def on_chain_end(self, outputs: Dict[str, Any], **kwargs: Any) -> None: """Print out that we finished a chain.""" print("\n\033[1m> Finished chain.\033[0m") # noqa: T201
[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)
[docs] def on_tool_end( self, output: Any, 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.""" output = str(output) if observation_prefix is not None: print_text(f"\n{observation_prefix}") print_text(output, color=color or self.color) if llm_prefix is not None: print_text(f"\n{llm_prefix}")
[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)
[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")