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This document was generated from the README in the Python GitHub repository.


To connect to Unleash, you'll need your Unleash API url (e.g. https://<your-unleash>/api) and a server-side API token (how do I create an API token?).


Coverage Status PyPI version PyPI - Python Version License: MIT

This is the Python client for Unleash. It implements Client Specifications 1.0 and checks compliance based on spec in unleash/client-specifications

What it supports:

  • Default activation strategies using 32-bit Murmurhash3
  • Custom strategies
  • Full client lifecycle:
    • Client registers with Unleash server
    • Client periodically fetches feature toggles and stores to on-disk cache
    • Client periodically sends metrics to Unleash Server
  • Tested on Linux (Ubuntu), OSX, and Windows

Check out the project documentation and the changelog.


Check out the package on Pypi!

pip install UnleashClient

For Flask Users

If you're looking into running Unleash from Flask, you might want to take a look at Flask-Unleash, the Unleash Flask extension. The extension builds upon this SDK to reduce the amount of boilerplate code you need to write to integrate with Flask. Of course, if you'd rather use this package directly, that will work too.



from UnleashClient import UnleashClient

client = UnleashClient(
custom_headers={'Authorization': '<API token>'})


For more information about configuring UnleashClient, check out the project reference docs!

Checking if a feature is enabled

A check of a simple toggle:


To supply application context, use the second positional argument:

app_context = {"userId": ""}
client.is_enabled("user_id_toggle", app_context)

Fallback function and default values

You can specify a fallback function for cases where the client doesn't recognize the toggle by using the fallback_function keyword argument:

def custom_fallback(feature_name: str, context: dict) -> bool:
return True

client.is_enabled("my_toggle", fallback_function=custom_fallback)

You can also use the fallback_function argument to replace the obsolete default_value keyword argument by using a lambda that ignores its inputs. Whatever the lambda returns will be used as the default value.

client.is_enabled("my_toggle", fallback_function=lambda feature_name, context: True)

The fallback function must accept the feature name and context as positional arguments in that order.

The client will evaluate the fallback function only if an exception occurs when calling the is_enabled() method. This happens when the client can't find the feature flag. The client may also throw other, general exceptions.

For more information about usage, see the Usage documentation.

Getting a variant

Checking for a variant:

context = {'userId': '2'}  # Context must have userId, sessionId, or remoteAddr.  If none are present, distribution will be random.

variant = client.get_variant("variant_toggle", context)

> {
> "name": "variant1",
> "payload": {
> "type": "string",
> "value": "val1"
> },
> "enabled": True
> }

For more information about variants, see the Variant documentation.

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