API 参考
LangChain Python API 完整参考手册
本 API 参考基于 LangChain v0.3，涵盖核心模块和常用集成。每个 API 页面包含类/函数签名、参数说明、返回值和代码示例。
API 分类索引
📦 核心模块
🚀 高级功能
快速查找
按字母索引
常用类快速链接
API 使用指南
安装 LangChain
bash
# 核心包
pip install langchain-core
# 完整包
pip install langchain
# 文本分割
pip install langchain-text-splitters
# 社区集成
pip install langchain-community核心导入模式
python
# 语言模型
from langchain_openai import ChatOpenAI
from langchain_anthropic import ChatAnthropic
from langchain_google_genai import ChatGoogleGenerativeAI
# 提示模板
from langchain_core.prompts import ChatPromptTemplate, PromptTemplate
from langchain_core.prompts import MessagesPlaceholder
# 链和运行
from langchain_core.runnables import (
RunnableLambda,
RunnableParallel,
RunnablePassthrough,
RunnableBranch
)
# 输出解析
from langchain_core.output_parsers import (
PydanticOutputParser,
JsonOutputParser,
StrOutputParser
)
# 工具
from langchain_core.tools import tool
from langchain_core.tools import StructuredTool
# 智能体
from langchain.agents import create_tool_calling_agent, AgentExecutor
# 文档加载
from langchain_community.document_loaders import (
TextLoader,
PyPDFLoader,
WebBaseLoader
)
# 文本分割
from langchain_text_splitters import (
RecursiveCharacterTextSplitter,
CharacterTextSplitter
)
# 向量存储
from langchain.vectorstores import Chroma, FAISS
from langchain_community.vectorstores import PineconeVectorStore
# 嵌入
from langchain_openai import OpenAIEmbeddings
from langchain_huggingface import HuggingFaceEmbeddings
# 检索
from langchain_core.retrievers import BaseRetriever
# 记忆
from langchain.memory import ConversationBufferMemory
from langchain_core.chat_history import (
BaseChatMessageHistory,
InMemoryChatMessageHistory
)
# 回调
from langchain_core.callbacks import BaseCallbackHandler
from langchain.callbacks import StdOutCallbackHandler
# 评估
from langchain_core.evaluators import StringEvaluator
from langchain_core.evaluators import load_evaluator
# LangGraph
from langgraph.graph import StateGraph, END
from langgraph.checkpoint.memory import MemorySaver