Source code for langchain.callbacks.stdout
"""Callback Handler that prints to std out."""
from typing import Any, Dict, List, Optional, Union
from langchain.callbacks.base import BaseCallbackHandler
from langchain.input import print_text
from langchain.schema import AgentAction, AgentFinish, LLMResult
[docs]class StdOutCallbackHandler(BaseCallbackHandler):
    """Callback Handler that prints to std out."""
    def __init__(self, color: Optional[str] = None) -> None:
        """Initialize callback handler."""
        self.color = color
[docs]    def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> None:
        """Print out the prompts."""
        pass
[docs]    def on_llm_end(self, response: LLMResult, **kwargs: Any) -> None:
        """Do nothing."""
        pass
[docs]    def on_llm_new_token(self, token: str, **kwargs: Any) -> None:
        """Do nothing."""
        pass
[docs]    def on_llm_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> None:
        """Do nothing."""
        pass
[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", "")
        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_chain_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> None:
        """Do nothing."""
        pass
[docs]    def on_tool_start(
        self,
        serialized: Dict[str, Any],
        input_str: str,
        **kwargs: Any,
    ) -> None:
        """Do nothing."""
        pass
[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 if color else self.color)
[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}")
        print_text(output, color=color if color else self.color)
        if llm_prefix is not None:
            print_text(f"\n{llm_prefix}")
[docs]    def on_tool_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> None:
        """Do nothing."""
        pass
[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 if color else 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 if self.color else color, end="\n")