Source code for whalrus.rules.rule_irv

# -*- coding: utf-8 -*-
Copyright Sylvain Bouveret, Yann Chevaleyre and Fran├žois Durand,,

This file is part of Whalrus.

Whalrus is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Whalrus is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
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from whalrus.rules.rule import Rule
from whalrus.rules.rule_iterated_elimination import RuleIteratedElimination
from whalrus.rules.rule_plurality import RulePlurality
from whalrus.eliminations.elimination import Elimination
from whalrus.eliminations.elimination_last import EliminationLast
from whalrus.priorities.priority import Priority

[docs]class RuleIRV(RuleIteratedElimination): """ Instant-Runoff Voting, also known as Alternative Vote, Single Transferable Vote, etc. Parameters ---------- args Cf. parent class. base_rule : Rule Default: :class:`RulePlurality`. elimination : Elimination Default: :class:`EliminationLast` with ``k=1``. kwargs Cf. parent class. Examples -------- At each round, the candidate with the worst Plurality score is eliminated. >>> rule = RuleIRV(['a > b > c', 'b > a > c', 'c > a > b'], weights=[2, 3, 4]) >>> rule.eliminations_[0].rule_.gross_scores_ {'a': 2, 'b': 3, 'c': 4} >>> rule.eliminations_[1].rule_.gross_scores_ {'b': 5, 'c': 4} >>> rule.eliminations_[2].rule_.gross_scores_ {'b': 9} >>> rule.winner_ 'b' An example using the tie-break: >>> rule = RuleIRV(['a > c > b', 'b > a > c', 'c > a > b'], weights=[1, 2, 1], ... tie_break=Priority.ASCENDING) >>> rule.eliminations_[0].rule_.gross_scores_ {'a': 1, 'b': 2, 'c': 1} >>> rule.eliminations_[1].rule_.gross_scores_ {'a': 2, 'b': 2} >>> rule.eliminations_[2].rule_.gross_scores_ {'a': 4} >>> rule.winner_ 'a' """ def __init__(self, *args, base_rule: Rule = None, elimination: Elimination = None, **kwargs): if base_rule is None: base_rule = RulePlurality() if elimination is None: elimination = EliminationLast(k=1) super().__init__(*args, base_rule=base_rule, elimination=elimination, **kwargs)