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
if TYPE_CHECKING:
    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")
[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")
[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: str,
        color: Optional[str] = None,
        observation_prefix: Optional[str] = None,