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How to install Langfuse Python SDK

Q: How to install Langfuse Python SDK

Install the Langfuse Python SDK using pip install langfuse. Then, initialize the client in your Python code with your API keys from environment variables using Langfuse(public_key=..., secret_key=...).

Quick answer

Install the Langfuse Python SDK using pip install langfuse. Then, initialize the client in your Python code with your API keys from environment variables using Langfuse(public_key=..., secret_key=...).

PREREQUISITES

Python 3.8+
Langfuse API keys (public and secret)
pip install langfuse

Setup

Install the Langfuse Python SDK via pip and set your API keys as environment variables for secure access.

bash

pip install langfuse

Step by step

Use the following Python code to initialize the Langfuse client and send a simple trace event.

python

import os
from langfuse import Langfuse

# Initialize Langfuse client with API keys from environment variables
langfuse = Langfuse(
    public_key=os.environ["LANGFUSE_PUBLIC_KEY"],
    secret_key=os.environ["LANGFUSE_SECRET_KEY"],
    host="https://cloud.langfuse.com"
)

# Example function to trace
@langfuse.observe()
def greet(name: str) -> str:
    return f"Hello, {name}!"

# Call the function
print(greet("World"))

output

Hello, World!

Common variations

You can use the @observe() decorator to trace multiple functions or use langfuse_context for context management. The SDK supports custom hosts if you run a self-hosted Langfuse instance.

python

from langfuse.decorators import observe, langfuse_context

@observe()
def add(a: int, b: int) -> int:
    return a + b

with langfuse_context():
    result = add(3, 4)
    print(result)

output

Troubleshooting

If you see authentication errors, verify your LANGFUSE_PUBLIC_KEY and LANGFUSE_SECRET_KEY environment variables are set correctly.
Ensure network connectivity to https://cloud.langfuse.com or your custom host.
Use pip show langfuse to confirm the SDK is installed.

✅

Key Takeaways

Install Langfuse SDK with pip install langfuse and set API keys via environment variables.
Use Langfuse(public_key=..., secret_key=...) to initialize the client in Python.
Leverage @observe() decorator to trace function calls automatically.
Check environment variables and network access if authentication or connectivity issues arise.

Verified 2026-04

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