如何将事件从工具中流式传输

前置条件

本指南假设您熟悉以下概念：

如果您有调用聊天模型、检索器或其他可运行对象的工具，您可能希望访问这些可运行对象的内部事件或使用其他属性对其进行配置。本指南将向您展示如何手动正确传递参数，以便使用astream_events()方法实现这一目标。

兼容性

如果您在 python<=3.10 中运行 async 代码，LangChain 无法自动传播配置（包括对 astream_events() 必要的回调）到子可运行对象。这是您可能无法看到自定义可运行对象或工具发出事件的常见原因。

如果您运行的是 python<=3.10，则需要在异步环境中手动将 RunnableConfig 对象传播到子可运行对象。关于如何手动传播配置的示例，请参阅下方 bar RunnableLambda 的实现。

如果您运行的是 Python>=3.11，RunnableConfig 将自动传播到异步环境中的子可运行对象。但是，如果您的代码可能在旧版 Python 版本中运行，手动传播 RunnableConfig 仍然是一个好主意。

本指南还需要 langchain-core>=0.2.16。

假设您有一个自定义工具，该工具调用一个链，通过提示聊天模型仅返回10个单词来压缩其输入，然后反转输出。首先，以简单的方式定义它：

选择聊天模型:

pip install -qU "langchain[openai]"

import getpass
import os

if not os.environ.get("OPENAI_API_KEY"):
  os.environ["OPENAI_API_KEY"] = getpass.getpass("Enter API key for OpenAI: ")

from langchain.chat_models import init_chat_model

model = init_chat_model("gpt-4o-mini", model_provider="openai")

from langchain_core.output_parsers import StrOutputParser
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.tools import tool


@tool
async def special_summarization_tool(long_text: str) -> str:
    """A tool that summarizes input text using advanced techniques."""
    prompt = ChatPromptTemplate.from_template(
        "You are an expert writer. Summarize the following text in 10 words or less:\n\n{long_text}"
    )

    def reverse(x: str):
        return x[::-1]

    chain = prompt | model | StrOutputParser() | reverse
    summary = await chain.ainvoke({"long_text": long_text})
    return summary

API 参考:StrOutputParser |聊天提示模板 |工具

直接调用工具效果很好：

LONG_TEXT = """
NARRATOR:
(Black screen with text; The sound of buzzing bees can be heard)
According to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because bees don't care what humans think is impossible.
BARRY BENSON:
(Barry is picking out a shirt)
Yellow, black. Yellow, black. Yellow, black. Yellow, black. Ooh, black and yellow! Let's shake it up a little.
JANET BENSON:
Barry! Breakfast is ready!
BARRY:
Coming! Hang on a second.
"""

await special_summarization_tool.ainvoke({"long_text": LONG_TEXT})

'.yad noitaudarg rof tiftuo sesoohc yrraB ;scisyhp seifed eeB'

但如果您想要访问聊天模型的原始输出而不是完整工具，您可以尝试使用 astream_events() 方法并查找 on_chat_model_end 事件。以下是发生的情况：

stream = special_summarization_tool.astream_events({"long_text": LONG_TEXT})

async for event in stream:
    if event["event"] == "on_chat_model_end":
        # Never triggers in python<=3.10!
        print(event)

你会注意到（除非你正在通过python>=3.11运行此指南），子运行中没有任何聊天模型事件被发出！

这是因为上面的示例未将工具的配置对象传递给内部链。要修复此问题，请重新定义您的工具以接受一个特殊参数，该参数的类型应为 RunnableConfig（更多详细信息请参阅本指南）。在执行为时，您还需要将该参数传递到内部链中：

from langchain_core.runnables import RunnableConfig


@tool
async def special_summarization_tool_with_config(
    long_text: str, config: RunnableConfig
) -> str:
    """A tool that summarizes input text using advanced techniques."""
    prompt = ChatPromptTemplate.from_template(
        "You are an expert writer. Summarize the following text in 10 words or less:\n\n{long_text}"
    )

    def reverse(x: str):
        return x[::-1]

    chain = prompt | model | StrOutputParser() | reverse
    # Pass the "config" object as an argument to any executed runnables
    summary = await chain.ainvoke({"long_text": long_text}, config=config)
    return summary

API 参考:可运行配置

现在用你的新工具尝试之前的 astream_events() 调用：

stream = special_summarization_tool_with_config.astream_events({"long_text": LONG_TEXT})

async for event in stream:
    if event["event"] == "on_chat_model_end":
        print(event)

{'event': 'on_chat_model_end', 'data': {'output': AIMessage(content='Bee defies physics; Barry chooses outfit for graduation day.', additional_kwargs={}, response_metadata={'stop_reason': 'end_turn', 'stop_sequence': None}, id='run-337ac14e-8da8-4c6d-a69f-1573f93b651e', usage_metadata={'input_tokens': 182, 'output_tokens': 19, 'total_tokens': 201, 'input_token_details': {'cache_creation': 0, 'cache_read': 0}}), 'input': {'messages': [[HumanMessage(content="You are an expert writer. Summarize the following text in 10 words or less:\n\n\nNARRATOR:\n(Black screen with text; The sound of buzzing bees can be heard)\nAccording to all known laws of aviation, there is no way a bee should be able to fly. Its wings are too small to get its fat little body off the ground. The bee, of course, flies anyway because bees don't care what humans think is impossible.\nBARRY BENSON:\n(Barry is picking out a shirt)\nYellow, black. Yellow, black. Yellow, black. Yellow, black. Ooh, black and yellow! Let's shake it up a little.\nJANET BENSON:\nBarry! Breakfast is ready!\nBARRY:\nComing! Hang on a second.\n", additional_kwargs={}, response_metadata={})]]}}, 'run_id': '337ac14e-8da8-4c6d-a69f-1573f93b651e', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['225beaa6-af73-4c91-b2d3-1afbbb88d53e']}

太棒了！这次触发了一个事件。

对于流式传输，astream_events() 会在可能时自动以启用流式传输的方式调用链中的内部可运行对象，因此如果您想要获取聊天模型生成的令牌流，只需过滤以查找 on_chat_model_stream 事件，无需其他更改：

stream = special_summarization_tool_with_config.astream_events({"long_text": LONG_TEXT})

async for event in stream:
    if event["event"] == "on_chat_model_stream":
        print(event)

{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content='', additional_kwargs={}, response_metadata={}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', usage_metadata={'input_tokens': 182, 'output_tokens': 2, 'total_tokens': 184, 'input_token_details': {'cache_creation': 0, 'cache_read': 0}})}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}
{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content='Bee', additional_kwargs={}, response_metadata={}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5')}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}
{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content=' defies physics;', additional_kwargs={}, response_metadata={}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5')}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}
{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content=' Barry chooses outfit for', additional_kwargs={}, response_metadata={}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5')}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}
{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content=' graduation day.', additional_kwargs={}, response_metadata={}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5')}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}
{'event': 'on_chat_model_stream', 'data': {'chunk': AIMessageChunk(content='', additional_kwargs={}, response_metadata={'stop_reason': 'end_turn', 'stop_sequence': None}, id='run-f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', usage_metadata={'input_tokens': 0, 'output_tokens': 17, 'total_tokens': 17, 'input_token_details': {}})}, 'run_id': 'f5e049f7-4e98-4236-87ab-8cd1ce85a2d5', 'name': 'ChatAnthropic', 'tags': ['seq:step:2'], 'metadata': {'ls_provider': 'anthropic', 'ls_model_name': 'claude-3-5-sonnet-20240620', 'ls_model_type': 'chat', 'ls_temperature': 0.0, 'ls_max_tokens': 1024}, 'parent_ids': ['51858043-b301-4b76-8abb-56218e405283']}

下一步

您现在已了解如何从工具中流式传输事件。接下来，请查看以下指南，了解更多关于使用工具的内容：

将运行时值传递给工具
将工具结果返回给模型
分发自定义回调事件

您也可以查看一些更具体的工具调用用途：

构建使用工具的链和智能体
从模型获取结构化输出

下一步​

下一步