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The reference implementation of the single transferable vote (STV) system used for student government elections at Carnegie Mellon University.
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CMU Fair Ranked Voting


The reference implementation of the single transferable vote (STV) system used for student government elections at Carnegie Mellon University.


The election classes and algorithm are located in A more formal declaration of the algorithm and election rules is located in the Additionally, provides a command-line interface to run elections:

usage: [-h] -s SEATS [-a ALPHANUMERIC] [-b BALLOTS] [-c] [-n NAME] [-r]

Configure and run an election. Ballots ranking candidates may be imported from
a CSV or TXT file, or manual input if no file is specified. The expected input
format for a candidate is 'uid' or optionally 'uid (name)'.

optional arguments:
  -h, --help            show this help message and exit
                        Alphanumeric string for breaking ties
  -b BALLOTS, --ballots BALLOTS
                        File/URL containing ballots
  -c, --disallow-nc-elimination
                        No Confidence cannot be eliminated
  -n NAME, --name NAME  Name of election
  -r, --disallow-random-tiebreak
                        Halt election instead of using random tiebreak
  -v, --verbose         Verbose printing of election results

required arguments:
  -s SEATS, --seats SEATS
                        Number of seats

Example: CMU Student Senate Election 2017

Twelve seat election with a randomly-sorted alphanumeric for final tiebreaks.

python -v -n 'CMU College of Engineering' -s 12 -a 'vrb4pes1t0xnm7jdf2k8cgzqloh9wyia5u63' -b ballots.csv

Example: CMU Student Body President Election 2017

One seat election with No Confidence unable to be eliminated and halts instead of random final tiebreak.

python -v -c -r -n 'CMU Student Body President' -s 1 -b ballots.csv


The included unit tests in can be run with:

python -m unittest -v tests

Frequently Asked Questions

Why was this created?

Senators in the Carnegie Mellon Student Senate are involved in many initiatives aimed at improving the student experience across the university and empowering change within student government. We care deeply about democracy and fairness in electoral systems, and we wanted to apply this to our campus. With no free and open-source STV program that was reliably-maintained and fit our needs, the best solution was to create our own. Devin Gund developed this election software with the help of Sushain Cherivirala, and together with many other dedicated students we converted our voting system to STV.

Can I use this to run elections?

Yes! This project is free and open-source software under the GPLv3 license. With the code and example bylaws, you can implement an STV system and bring fair ranked voting to your organization.

Why did you choose STV?

The decision to investigate using instant-runoff voting (IRV) for single-seat executive positions was made by a previous student body executive branch. When we joined the Senate, we worked to move forward with these reforms and apply them to all elections. The simplest choice was to use STV, as it serves as an extension of IRV for multi-seat elections.

STV allows voters to rank their preferred candidates and have their votes transfer as candidates are eliminated or elected. This leads to approximately proportional representation and avoids the spoiler effect of splitting votes between similar candidates. However, STV has its issues, and no voting system is perfect.

Why should I care about a voting system?

Simply put, our elections allocate power and dictate policy, and our voting systems are what decide these elections. Traditional first-past-the-post voting has many flaws, and maybe we can come up with solutions that make our elections, and therefore our governments, even more representative, transparent, and inclusive.

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