Quickstart

This quickstart helps you to integrate your LLM application with Langfuse. It will log a single LLM call to get started.

Create new project in Langfuse

Create Langfuse account (opens in a new tab) or self-host
Create a new project
Create new API credentials in the project settings

Log your first LLM call to Langfuse

The @observe() decorator makes it easy to trace any Python LLM application. In this quickstart we also use the Langfuse OpenAI integration to automatically capture all model parameters.

Not using OpenAI? Switch to the "Python Decorator + any LLM" tab.

pip install langfuse openai

.env

LANGFUSE_SECRET_KEY="sk-lf-..."
LANGFUSE_PUBLIC_KEY="pk-lf-..."
LANGFUSE_HOST="https://cloud.langfuse.com" # 🇪🇺 EU region
# LANGFUSE_HOST="https://us.cloud.langfuse.com" # 🇺🇸 US region

main.py

from langfuse.decorators import observe
from langfuse.openai import openai # OpenAI integration
 
@observe()
def story():
    return openai.chat.completions.create(
        model="gpt-3.5-turbo",
        max_tokens=100,
        messages=[
          {"role": "system", "content": "You are a great storyteller."},
          {"role": "user", "content": "Once upon a time in a galaxy far, far away..."}
        ],
    ).choices[0].message.content
 
@observe()
def main():
    return story()
 
main()