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LaunchDarkly SDK for Python

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Supported Python versions

This version of the LaunchDarkly SDK is compatible with Python 2.7, and Python 3.3 through 3.7.

Quick setup

  1. Install the Python SDK with pip

     pip install ldclient-py
  2. Configure the library with your sdk key:

     import ldclient
  3. Get the client:

     ldclient.set_sdk_key("your sdk key")
     client = ldclient.get()

HTTPS proxy

Python's standard HTTP library provides built-in support for the use of a HTTPS proxy. If the HTTPS_PROXY environment variable is present then the SDK will proxy all network requests through the URL provided.

How to set the HTTPS_PROXY environment variable on Mac/Linux systems:


How to set the HTTPS_PROXY environment variable on Windows systems:


Or it can be set from within python:

os.environ["https_proxy"] = ""

If your proxy requires authentication then you can prefix the URN with your login information:




Your first feature flag

  1. Create a new feature flag on your dashboard

  2. In your application code, use the feature's key to check whether the flag is on for each user:

     if client.variation("your.flag.key", {"key": ""}, False):
         # application code to show the feature
         # the code to run if the feature is off

Supported Python versions

The SDK is tested with the most recent patch releases of Python 2.7, 3.3, 3.4, 3.5, and 3.6. Python 2.6 is no longer supported.

Learn more

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


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.

Test Coverage The Code Climate coverage does not include the coverage provided by this integration test harness.


See CONTRIBUTING for more information.

About LaunchDarkly

  • 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
  • Explore LaunchDarkly