Standalone Python 3 scripts for counting various preferential voting elections, including:
- Wright STV
- Single Transferable Vote (weighted inclusive Gregory)
- Instant Runoff Voting (aka. the Alternative Vote)
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python -m pyRCV.irv --election election.blt
Takes as input an OpenSTV blt file, and calculates the winner under IRV.
Supply the --npr option to use non-proportional representation, iteratively removing the winner from each round to produce an ordered list of winners – as for the filling of casual vacancies.
python -m pyRCV.stv --election election.blt
Takes as input an OpenSTV blt file, and calculates the winners under STV.
The counting method is highly configurable to a wide range of STV implementations. See ./stv.py --help for more information.
python -m pyRCV.wright_stv --election election.blt --quota-prog
The same for Wright STV. Note that Wright STV uses a progressively-reducing quota, so --quota-prog should be specified.
python -m pyRCV.meek_stv --election election.blt --quota geq-hb --quota-prog --nums float
The same for Meek STV. Note that Meek STV uses a progressively-reducing quota (--quota-prog), and the quota is the unrounded Droop (Hagenbach-Bischoff) quota (--quota geq-hb). Note also that Meek STV is quite computationally expensive, so the --nums float option is recommended to disable rational arithmetic.
These scripts can be used to perform a Hare-Clark-style countback to fill vacancies. Firstly, we must capture the quota of votes used to finally elect the candidate causing the vacancy:
python -m pyRCV.wright_stv --election election.blt --countback CandidateName countback.blt
This command will output a new blt file containing only this quota of votes. We can then run an instant-runoff election with these votes.
python -m pyRCV.irv --election countback.blt
If some candidates have chosen not to contest the countback, you can add an -ID line into the blt file in the withdrawn candidates block, where ID is the 1-indexed position of the candidate in the candidate list.
On an HP Pavilion dv7-6108tx, the 49,702-vote EVE Online CSM8 election is processed by the EVE Online reference implementation of Wright STV in an average of 6.37 seconds. (±0.04s) The same election is processed by pyRCV's equivalent wright_stv.py --fast --nums float --noround in an average of 2.34 seconds! (±0.02s) For comparison, using increased-accuracy rational arithmetic (omitting --num float) takes an average of 8.64 seconds. (±0.04s)