Source code for langchain_core.tracers.stdout

import json
from typing import Any, Callable, List

from langchain_core.tracers.base import BaseTracer
from langchain_core.tracers.schemas import Run
from langchain_core.utils.input import get_bolded_text, get_colored_text


[docs]def try_json_stringify(obj: Any, fallback: str) -> str: """ Try to stringify an object to JSON. Args: obj: Object to stringify. fallback: Fallback string to return if the object cannot be stringified. Returns: A JSON string if the object can be stringified, otherwise the fallback string. """ try: return json.dumps(obj, indent=2, ensure_ascii=False) except Exception: return fallback
[docs]def elapsed(run: Any) -> str: """Get the elapsed time of a run. Args: run: any object with a start_time and end_time attribute. Returns: A string with the elapsed time in seconds or milliseconds if time is less than a second. """ elapsed_time = run.end_time - run.start_time milliseconds = elapsed_time.total_seconds() * 1000 if milliseconds < 1000: return f"{milliseconds:.0f}ms" return f"{(milliseconds / 1000):.2f}s"
[docs]class FunctionCallbackHandler(BaseTracer): """Tracer that calls a function with a single str parameter.""" name: str = "function_callback_handler"
[docs] def __init__(self, function: Callable[[str], None], **kwargs: Any) -> None: super().__init__(**kwargs) self.function_callback = function
def _persist_run(self, run: Run) -> None: pass
[docs] def get_parents(self, run: Run) -> List[Run]: parents = [] current_run = run while current_run.parent_run_id: parent = self.run_map.get(str(current_run.parent_run_id)) if parent: parents.append(parent) current_run = parent else: break return parents
[docs] def get_breadcrumbs(self, run: Run) -> str: parents = self.get_parents(run)[::-1] string = " > ".join( f"{parent.run_type}:{parent.name}" if i != len(parents) - 1 else f"{parent.run_type}:{parent.name}" for i, parent in enumerate(parents + [run]) ) return string
# logging methods def _on_chain_start(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) run_type = run.run_type.capitalize() self.function_callback( f"{get_colored_text('[chain/start]', color='green')} " + get_bolded_text(f"[{crumbs}] Entering {run_type} run with input:\n") + f"{try_json_stringify(run.inputs, '[inputs]')}" ) def _on_chain_end(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) run_type = run.run_type.capitalize() self.function_callback( f"{get_colored_text('[chain/end]', color='blue')} " + get_bolded_text( f"[{crumbs}] [{elapsed(run)}] Exiting {run_type} run with output:\n" ) + f"{try_json_stringify(run.outputs, '[outputs]')}" ) def _on_chain_error(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) run_type = run.run_type.capitalize() self.function_callback( f"{get_colored_text('[chain/error]', color='red')} " + get_bolded_text( f"[{crumbs}] [{elapsed(run)}] {run_type} run errored with error:\n" ) + f"{try_json_stringify(run.error, '[error]')}" ) def _on_llm_start(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) inputs = ( {"prompts": [p.strip() for p in run.inputs["prompts"]]} if "prompts" in run.inputs else run.inputs ) self.function_callback( f"{get_colored_text('[llm/start]', color='green')} " + get_bolded_text(f"[{crumbs}] Entering LLM run with input:\n") + f"{try_json_stringify(inputs, '[inputs]')}" ) def _on_llm_end(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) self.function_callback( f"{get_colored_text('[llm/end]', color='blue')} " + get_bolded_text( f"[{crumbs}] [{elapsed(run)}] Exiting LLM run with output:\n" ) + f"{try_json_stringify(run.outputs, '[response]')}" ) def _on_llm_error(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) self.function_callback( f"{get_colored_text('[llm/error]', color='red')} " + get_bolded_text( f"[{crumbs}] [{elapsed(run)}] LLM run errored with error:\n" ) + f"{try_json_stringify(run.error, '[error]')}" ) def _on_tool_start(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) self.function_callback( f'{get_colored_text("[tool/start]", color="green")} ' + get_bolded_text(f"[{crumbs}] Entering Tool run with input:\n") + f'"{run.inputs["input"].strip()}"' ) def _on_tool_end(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) if run.outputs: self.function_callback( f'{get_colored_text("[tool/end]", color="blue")} ' + get_bolded_text( f"[{crumbs}] [{elapsed(run)}] Exiting Tool run with output:\n" ) + f'"{run.outputs["output"].strip()}"' ) def _on_tool_error(self, run: Run) -> None: crumbs = self.get_breadcrumbs(run) self.function_callback( f"{get_colored_text('[tool/error]', color='red')} " + get_bolded_text(f"[{crumbs}] [{elapsed(run)}] ") + f"Tool run errored with error:\n" f"{run.error}" )
[docs]class ConsoleCallbackHandler(FunctionCallbackHandler): """Tracer that prints to the console.""" name: str = "console_callback_handler"
[docs] def __init__(self, **kwargs: Any) -> None: super().__init__(function=print, **kwargs)