LaunchDarkly is a feature management platform that serves trillions of feature flags daily to help teams build better software, faster. Get started using LaunchDarkly today!

This version of the LaunchDarkly SDK is compatible with Python 3.10+.

Refer to the SDK reference guide for instructions on getting started with using the SDK.

An async implementation, AsyncLDClient, is available for use with asyncio-based applications. It uses aiohttp for HTTP and requires installing the optional async extra:

pip install launchdarkly-server-sdk[async]

import asyncio
from ldclient import Config, Context
from ldclient.async_client import AsyncLDClient

async def main():
    async with AsyncLDClient(Config("sdk-key")) as client:
        value = await client.variation("my-flag", Context.create("user-key"), False)
        print(value)

asyncio.run(main())

AsyncLDClient runs on the caller's event loop. It targets a single event loop and is not thread-safe. Use one client for the whole application.

The constructor does not need a running event loop. So you can create the client once, before the application forks or preloads its workers. Then start the client on each worker's event loop with await client.start(). You can also use async with AsyncLDClient(config) as client:, which starts and closes the client for you.

This model fits ASGI servers. Create the client at application startup, and start it in the ASGI lifespan handler.

Read our documentation for in-depth instructions on configuring and using LaunchDarkly. You can also head straight to the complete reference guide for this SDK.

Generated API documentation is on readthedocs.io.

We run integration tests for all our SDKs using a centralized test harness. This approach gives us the ability to test for consistency across SDKs, as well as test networking behavior in a long-running application. These tests cover each method in the SDK, and verify that event sending, flag evaluation, stream reconnection, and other aspects of the SDK all behave correctly.

We encourage pull requests and other contributions from the community. Check out our contributing guidelines for instructions on how to contribute to this SDK.

LaunchDarkly uses the SLSA framework (Supply-chain Levels for Software Artifacts) to help developers make their supply chain more secure by ensuring the authenticity and build integrity of our published SDK packages. To learn more, see the provenance guide.

• LaunchDarkly is a continuous delivery platform that provides feature flags as a service and allows developers to iterate quickly and safely. We allow you to easily flag your features and manage them from the LaunchDarkly dashboard. With LaunchDarkly, you can:
  • Roll out a new feature to a subset of your users (like a group of users who opt-in to a beta tester group), gathering feedback and bug reports from real-world use cases.
  • Gradually roll out a feature to an increasing percentage of users, and track the effect that the feature has on key metrics (for instance, how likely is a user to complete a purchase if they have feature A versus feature B?).
  • Turn off a feature that you realize is causing performance problems in production, without needing to re-deploy, or even restart the application with a changed configuration file.
  • Grant access to certain features based on user attributes, like payment plan (eg: users on the ‘gold’ plan get access to more features than users in the ‘silver’ plan). Disable parts of your application to facilitate maintenance, without taking everything offline.
• LaunchDarkly provides feature flag SDKs for a wide variety of languages and technologies. Read our documentation for a complete list.
• Explore LaunchDarkly
  • launchdarkly.com for more information
  • docs.launchdarkly.com for our documentation and SDK reference guides
  • apidocs.launchdarkly.com for our API documentation
  • blog.launchdarkly.com for the latest product updates