pref_voting 1.14.3

pref_voting is a Python package that contains tools to reason about elections and margin graphs, and implementations of voting methods.

pref_voting

Installation

The package can be installed using the pip3 package manager:

pip3 install pref_voting

Note: If you have both Python 2 and Python 3 installed on your system, make sure to use pip3 instead of pip to install packages for Python 3. Alternatively, you can use python3 -m pip to ensure you're using the correct version of pip. If you have modified your system's defaults or soft links, adjust accordingly.

Documentation

Online documentation is available at https://pref-voting.readthedocs.io.

Example Usage

A profile (of linear orders over the candidates) is created by initializing a Profile class object. Simply provide a list of rankings (each ranking is a tuple of numbers) and a list giving the number of voters with each ranking:

from pref_voting.profiles import Profile

rankings = [
    (0, 1, 2, 3), # candidate 0 is ranked first, candidate 1 is ranked second, candidate 2 is ranked 3rd, and candidate 3 is ranked last.
    (2, 3, 1, 0), 
    (3, 1, 2, 0), 
    (1, 2, 0, 3), 
    (1, 3, 2, 0)]

rcounts = [5, 3, 2, 4, 3] # 5 voters submitted the first ranking ((0, 1, 2, 3)), 3 voters submitted the second ranking, and so on.

prof = Profile(rankings, rcounts=rcounts)

prof.display() # display the profile

The function generate_profile is used to generate a profile for a given number of candidates and voters:

from pref_voting.generate_profiles import generate_profile

# generate a profile using the Impartial Culture probability model
prof = generate_profile(3, 4) # prof is a Profile object with 3 candidates and 4 voters

# generate a profile using the Impartial Anonymous Culture probability model
prof = generate_profile(3, 4, probmod = "IAC") # prof is a Profile object with 3 candidates and 4 voters 

To use one of the many voting methods, import the function from pref_voting.voting_methods and apply it to the profile:

from pref_voting.generate_profiles import generate_profile
from pref_voting.voting_methods import *

prof = generate_profile(3, 4) # create a profile with 3 candidates and 4 voters
split_cycle(prof) # returns the sorted list of winning candidates
split_cycle.display(prof) # display the winning candidates

Consult the documentation https://pref-voting.readthedocs.io for a complete overview of the package.

Testing

To ensure that the package is working correctly, you can run the test suite using pytest. The test files are located in the tests directory. Follow the instructions below based on your setup.

Prerequisites

• Python 3.8 or higher: Ensure you have a compatible version of Python installed.
• pytest: Install pytest if it's not already installed.

Running the tests

If you are using Poetry to manage your dependencies, run the tests with:

poetry run pytest

From the command line, run:

pytest

For more detailed output, add the -v or --verbose flag:

pytest -v

Questions?

Feel free to send an email if you have questions about the project.

License

MIT