florian-lackner / abcvoting

Python implementations of approval-based committee (multi-winner) voting rules

abcvoting

• Documentation
• Installation
• How to cite the abcvoting library
• Acknowledgements and contributors

A Python library of approval-based committee (ABC) rules

Approval-based committee rules (ABC rules) are voting methods for selecting a committee, i.e., a fixed-size subset of candidates. ABC rules are also known as approval-based multi-winner rules. The input of such rules are approval ballots. We recommend the book (Multi-Winner Voting with Approval Preferences) by Lackner and Skowron [2] as a detailed introduction to ABC rules and related research directions. In addition, the survey by Faliszewski et al. [1] is useful as a more general introduction to committee voting (not limited to approval ballots).

The following ABC rules are implemented:

• Approval Voting (AV)

• Satisfaction Approval Voting (SAV)

• Proportional Approval Voting (PAV)

• Sequential Proportional Approval Voting (seq-PAV)

• Reverse Sequential Proportional Approval Voting (revseq-PAV)

• Approval Chamberlin-Courant (CC)

• Phragmén's sequential rule

• Monroe's rule

• Minimax Approval Voting (MAV)

• Greedy Monroe

• Method of Equal Shares (Rule X)

• Phragmén's First Method (Eneström's Method)

• and many more ...

Installation

As simple as:

pip install abcvoting

Further details can be found here.

Development

Install all dependencies including development requirements and the abcvoting package in development mode:

pip install -e .[dev]

Basic unit tests can be run by excluding tests which require additional dependencies:

pytest  -m "not mipgurobi and not gmpy2 and not slow" tests/

For development, configure the black formatter and pre-commit hooks - see below. Also installing all optional dependencies is recommended.

A development package is build for every commit on the master branch and uploaded to the test instance of PyPI. It can be installed using the following command:

python3 -m pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple abcvoting

Black formatting

Code needs to be formatted using the black formatter. This is checked by Github actions. Configure your editor to run the black formatter.

Pre-commit hooks

Pre-commit hooks are not required, but they are recommended for development. Pre-commit is used to manage and maintain pre-commit hooks. Install pre-commit (e.g. via apt, conda or pip) and then run $ pre-commit install to install the hooks.

References

[1] Piotr Faliszewski, Piotr Skowron, Arkadii Slinko, and Nimrod Talmon. Multiwinner voting: A new challenge for social choice theory. In Ulle Endriss, editor, Trends in Computational Social Choice, chapter 2, pages 27–47. AI Access, 2017. http://research.illc.uva.nl/COST-IC1205/BookDocs/Chapters/TrendsCOMSOC-02.pdf

[2] Lackner, Martin, and Piotr Skowron. "Multi-Winner Voting with Approval Preferences". arXiv preprint arXiv:2007.01795. 2020. https://arxiv.org/abs/2007.01795