eiriks / python3-vote

Python 3 version of Python Vote Core (https://github.com/bradbeattie/python-vote-core)

Python Vote Core

python-vote-core implements various electoral methods, providing the results calculated off a provided set of ballots and options.

• Project page: http://github.com/bradbeattie/python-vote-core
• Issue tracker: http://github.com/bradbeattie/python-vote-core/issues
• Example usage: http://modernballots.com

Note on this copy of the code ("python3-vote")

I have no experience in porting Python from 2.x to 3.x, but needed this for an experiment in python 3. I've tried to change as little as possible (print to print(), iteritems() to items(), added some [lists](http://stackoverflow.com/questions/24291604/find-the-length-of-a-filter-object-in-python-3) around statements trying to get the len of filters, etc).

I'b be very happy If someone with more python experience than me took a look at this, and reviewed the code for any mistakes.

-Eirik (not the original author)

Methods implemented

• Single Winner Methods
  • Plurality (aka first-past-the-post or fptp)
  • Instant-Runoff Voting (aka IRV)
  • Schulze Method (aka Beatpath)
• Multiple Winner Methods
  • Plurality at large (aka block voting)
  • Single Transferable Vote (aka STV)
  • Schulze STV
• Ordering Methods
  • Schulze Proportional Representation
  • Schulze Nonproportional Representation

Basic Usage

Schulze method example:

>>> from pyvotecore.schulze_method import SchulzeMethod
>>> from pyvotecore.condorcet import CondorcetHelper
>>> ballots = [
...   { "count":3, "ballot":[["A"], ["C"], ["D"], ["B"]] },
...   { "count":9, "ballot":[["B"], ["A"], ["C"], ["D"]] },
...   { "count":8, "ballot":[["C"], ["D"], ["A"], ["B"]] },
...   { "count":5, "ballot":[["D"], ["A"], ["B"], ["C"]] },
...   { "count":5, "ballot":[["D"], ["B"], ["C"], ["A"]] }
... ]
>>> SchulzeMethod(ballots, ballot_notation = CondorcetHelper.BALLOT_NOTATION_GROUPING).as_dict()
{'actions': [{'edges': {('A', 'B')}},
  {'edges': {('A', 'C')}},
  {'nodes': {'A'}},
  {'edges': {('B', 'C')}},
  {'nodes': {'B', 'D'}}],
 'candidates': {'A', 'B', 'C', 'D'},
 'pairs': {('A', 'B'): 16,
  ('A', 'C'): 17,
  ('A', 'D'): 12,
  ('B', 'A'): 14,
  ('B', 'C'): 19,
  ('B', 'D'): 9,
  ('C', 'A'): 13,
  ('C', 'B'): 11,
  ('C', 'D'): 20,
  ('D', 'A'): 18,
  ('D', 'B'): 21,
  ('D', 'C'): 10},
 'strong_pairs': {('A', 'B'): 16,
  ('A', 'C'): 17,
  ('B', 'C'): 19,
  ('C', 'D'): 20,
  ('D', 'A'): 18,
  ('D', 'B'): 21},
 'winner': 'C'}