PolicyEngine Core

A fork of OpenFisca-Core that powers PolicyEngine country models (policyengine-uk, policyengine-us, policyengine-canada, policyengine-il, policyengine-ng) and the downstream apps and APIs. Provides the simulation engine, parameter tree, variable system, and reform machinery that each country package builds on top of.

Install

pip install policyengine-core

Supports Python 3.11–3.14.

Usage

Most users reach this package transitively through a country model. Import directly if you're building a new country model, writing a reform, or extending the core:

from policyengine_core.simulations import Simulation
from policyengine_core.reforms import Reform

See the documentation for API reference and tutorials.

Development

# Install dev dependencies (uses uv)
make install

# Run the full test suite
make test

# Run a single test
uv run pytest tests/core/test_file.py::test_name -v

# Format before committing (CI enforces)
make format

# Lint GitHub Actions workflows after editing .github/, from the repo root
# (CI enforces; install shellcheck and pyflakes so actionlint also checks
# run: scripts)
uvx --from actionlint-py==1.7.12.25 actionlint

Always use uv run for Python commands; bare python / pytest / pip may pick up the wrong environment.

Contributions: see CONTRIBUTING.md for branching, PR conventions, and the towncrier changelog.d/ workflow. Default branch is master.

License

Distributed under the AGPL License. See LICENSE for details.

Acknowledgements

• Forked from OpenFisca-Core.
• README template adapted from Othneil Drew's Best-README-Template.