harness-featureflags
Feature flag server SDK for python
Decision gist · record as of 2026-08-14
Yes, if you are using the Harness Feature Flags platform. The SDK is actively maintained, has low install friction, permissive licensing, and no known vulnerabilities. It is the canonical way to integrate Python applications with Harness flags. Not relevant if you use a different feature flag platform or manage flags in-process.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.5 or newer; Harness Feature Flags platform account and server SDK key to connect.
- Low install friction with a pure-Python wheel distribution.
- Active maintenance with recent releases; last commit on 2026-08-03.
License · maintenance · safety
Apache Software License 2.0 (permissive) — Apache Software License 2.0 (permissive) allows commercial use, modification, and distribution with minimal restrictions—suitable for most production environments.
last release 2026-04-09 (127 days) · last repo commit 2026-08-03 · 5 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 400,366 downloads/mo, #6,941 on PyPI
Alternatives
Verify before relying
pip install harness-featureflags
from featureflags.client import CfClient
from featureflags.evaluations.auth_target import Target
client = CfClient(apiKey="your-api-key")
target = Target(identifier="user_1", name="User 1")
result = client.bool_variation("flag-name", target, False)
print(result)- Performance characteristics under high-volume flag evaluations or large target populations.
- Behavior and fallback handling when the Harness platform is unreachable after retries exhausted.
- Thread-safety guarantees for concurrent flag evaluation calls.
What it is and what it does
This is the official Python SDK for integrating with Harness Feature Flags, a platform for managing feature toggles and A/B tests. The SDK connects to the Harness service, downloads flag definitions, and evaluates them locally based on target attributes and rules. It supports streaming updates so flag changes on the platform are reflected in real time without polling. The SDK handles caching, retry logic, and metrics reporting back to the platform.
You instantiate a client with an API key, create target objects representing users or entities, and call variation methods (bool_variation, int_variation, string_variation, etc.) to get the flag value for that target. The SDK applies rules, percentage rollouts, and custom targeting logic server-side and caches the results locally. It's designed for server-side use where you control the SDK lifecycle and have a persistent connection to the Harness backend.
Use it for
- Roll out new features gradually to a percentage of users without redeploying code.
- Run A/B tests by serving different flag variations to different user segments based on custom attributes.
- Kill-switch critical features in production by toggling a flag without a code push.
- Manage feature access by role or organization using target attributes and flag rules.
- Experiment with performance-impacting changes by enabling them for a subset of targets first.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you are using the Harness Feature Flags platform.
The SDK is actively maintained, has low install friction, permissive licensing, and no known vulnerabilities. It is the canonical way to integrate Python applications with Harness flags. Not relevant if you use a different feature flag platform or manage flags in-process.
Install
harness-featureflags on PyPI
Before you install
Low install friction with a pure-Python wheel distribution. Active maintenance with recent releases; last commit on 2026-08-03. Seven runtime dependencies (httpx, pyjwt, attrs, mmh3, requests, tenacity, typing-extensions) are all stable, widely-used libraries.
Requires Python 3.5 or newer; Harness Feature Flags platform account and server SDK key to connect.
License in practice
Apache Software License 2.0 (permissive) allows commercial use, modification, and distribution with minimal restrictions—suitable for most production environments.
Quickstart
pip install harness-featureflags
from featureflags.client import CfClient
from featureflags.evaluations.auth_target import Target
client = CfClient(apiKey="your-api-key")
target = Target(identifier="user_1", name="User 1")
result = client.bool_variation("flag-name", target, False)
print(result)Verify before relying
- Performance characteristics under high-volume flag evaluations or large target populations.
- Behavior and fallback handling when the Harness platform is unreachable after retries exhausted.
- Thread-safety guarantees for concurrent flag evaluation calls.
Package facts
| License | Apache Software License 2.0 permissive |
| Python support | Supports the current Python release >=3.5 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 7 packageshttpxpyjwtattrsmmh3requeststenacitytyping-extensions |
| Maintenance | Actively maintained 127 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 400,366 / month, #6,941 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 2 - Pre-AlphaIntended Audience :: DevelopersLicense :: OSI Approved :: Apache Software LicenseNatural Language :: EnglishProgramming Language :: Python :: 3Programming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8 |
Evidence: harness_featureflags-1.7.5-py2.py3-none-any.whl
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See also UnleashClient · statsig · yggdrasil-engine · launchdarkly-server-sdk · django-waffle · flagsmith-flag-engine · django-flags · flagsmith · openfeature-sdk