LangChain Install & Auth

Overview

Set up LangChain SDK and configure LLM provider authentication credentials.

Prerequisites

• Python 3.9+ or Node.js 18+
• Package manager (pip, poetry, or npm)
• LLM provider account (OpenAI, Anthropic, Google, etc.)
• API key from your LLM provider dashboard

Instructions

Step 1: Install LangChain Core

# Python (recommended)
pip install langchain langchain-core langchain-community

# Or with specific providers
pip install langchain-openai langchain-anthropic langchain-google-genai

# Node.js
npm install langchain @langchain/core @langchain/community

Step 2: Configure Authentication

# OpenAI
export OPENAI_API_KEY="your-openai-key"

# Anthropic
export ANTHROPIC_API_KEY="your-anthropic-key"

# Google
export GOOGLE_API_KEY="your-google-key"

# Or create .env file
echo 'OPENAI_API_KEY=your-openai-key' >> .env

Step 3: Verify Connection

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(model="gpt-4o-mini")
response = llm.invoke("Say hello!")
print(response.content)

Output

• Installed LangChain packages in virtual environment
• Environment variables or .env file with API keys
• Successful connection verification output

Error Handling

Error	Cause	Solution
Invalid API Key	Incorrect or expired key	Verify key in provider dashboard
Rate Limited	Exceeded quota	Check quota limits, implement backoff
Network Error	Firewall blocking	Ensure outbound HTTPS allowed
Module Not Found	Installation failed	Run pip install again, check Python version
Provider Error	Service unavailable	Check provider status page

Examples

Python Setup (OpenAI)

import os
from langchain_openai import ChatOpenAI

# Ensure API key is set
assert os.environ.get("OPENAI_API_KEY"), "Set OPENAI_API_KEY"

llm = ChatOpenAI(
    model="gpt-4o-mini",
    temperature=0.7,
    max_tokens=1000
)

Python Setup (Anthropic)

from langchain_anthropic import ChatAnthropic

llm = ChatAnthropic(
    model="claude-3-5-sonnet-20241022",
    temperature=0.7
)

TypeScript Setup

import { ChatOpenAI } from "@langchain/openai";

const llm = new ChatOpenAI({
  modelName: "gpt-4o-mini",
  temperature: 0.7
});

Resources

• LangChain Documentation
• LangChain JS/TS
• OpenAI API Keys
• Anthropic Console

Next Steps

After successful auth, proceed to langchain-hello-world for your first chain.