LangChain All In One

LangChain All In One

LangChain is a framework for building agents and LLM-powered applications. It helps you chain together interoperable components and third-party integrations to simplify AI application development – all while future-proofing decisions as the underlying technology evolves.

LangChain 是一个用于构建智能体和基于 LLM 的应用程序的框架。它可以帮助您将可互操作的组件和第三方集成连接起来，从而简化 AI 应用程序的开发——同时还能随着底层技术的演进，确保您的决策能够面向未来。

# Python pip
$ pip install langchain

https://github.com/langchain-ai/langchain

# pip install -qU langchain "langchain[anthropic]"
from langchain.agents import create_agent

def get_weather(city: str) -> str:
    """Get weather for a given city."""
    return f"It's always sunny in {city}!"

agent = create_agent(
    model="claude-sonnet-4-5-20250929",
    tools=[get_weather],
    system_prompt="You are a helpful assistant",
)

# Run the agent
agent.invoke(
    {"messages": [{"role": "user", "content": "what is the weather in sf"}]}
)

https://docs.langchain.com/oss/python/langchain/overview

demos

import * as z from "zod";
// npm install @langchain/anthropic to call the model
import { createAgent, tool } from "langchain";

const getWeather = tool(
  ({ city }) => `It's always sunny in ${city}!`,
  {
    name: "get_weather",
    description: "Get the weather for a given city",
    schema: z.object({
      city: z.string(),
    }),
  },
);

const agent = createAgent({
  model: "claude-sonnet-4-5-20250929",
  tools: [getWeather],
});

console.log(
  await agent.invoke({
    messages: [{ role: "user", content: "What's the weather in Tokyo?" }],
  })
);

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wiki

LangChain is a software framework that helps facilitate the integration of large language models (LLMs) into applications. As a language model integration framework, LangChain's use-cases largely overlap with those of language models in general, including document analysis and summarization, chatbots, and code analysis.

LangChain 是一个软件框架，有助于将大型语言模型 (LLM) 集成到应用程序中。作为一个语言模型集成框架，LangChain 的用例与一般语言模型的用例大体重叠，包括文档分析和摘要、聊天机器人和代码分析。

https://en.wikipedia.org/wiki/LangChain

LangGraph

https://docs.langchain.com/oss/javascript/langgraph/overview

refs

https://www.langchain.com/

https://smith.langchain.com/

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