Source code for whalrus.rules.rule_veto

# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and Fran├žois Durand
sylvain.bouveret@imag.fr, yann.chevaleyre@dauphine.fr, fradurand@gmail.com

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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Whalrus.  If not, see <http://www.gnu.org/licenses/>.
"""
import logging
from whalrus.rules.rule_score_num_average import RuleScoreNumAverage
from whalrus.scorers.scorer import Scorer
from whalrus.scorers.scorer_veto import ScorerVeto
from whalrus.converters_ballot.converter_ballot_to_veto import ConverterBallotToVeto
from whalrus.utils.utils import cached_property, NiceDict
from whalrus.converters_ballot.converter_ballot import ConverterBallot


[docs]class RuleVeto(RuleScoreNumAverage): """ The veto rule. Parameters ---------- args Cf. parent class. converter : ConverterBallot Default: :class:`ConverterBallotToVeto`. scorer : Scorer Default: :class:`ScorerVeto`. kwargs Cf. parent class. Examples -------- >>> RuleVeto(['a', 'b', 'b', 'c', 'c']).winner_ 'a' """ def __init__(self, *args, converter: ConverterBallot = None, scorer: Scorer = None, **kwargs): if converter is None: converter = ConverterBallotToVeto() if scorer is None: scorer = ScorerVeto() super().__init__(*args, converter=converter, scorer=scorer, **kwargs) def _check_profile(self, candidates: set) -> None: if any([len(b.candidates) > 1 and b.candidates != candidates for b in self.profile_converted_]): logging.warning('Some ballots do not have the same set of candidates as the whole election.') @cached_property def _gross_scores_and_weights_quicker_(self) -> dict: if not isinstance(self.scorer, ScorerVeto): return self._gross_scores_and_weights_ # If it is a ScorerVeto, we have a quicker method. gross_scores = NiceDict({c: 0 for c in self.candidates_}) total_weight = 0 for ballot, weight, _ in self.profile_converted_.items(): if ballot.candidate is None: if self.scorer.count_abstention: total_weight += weight continue gross_scores[ballot.candidate] -= weight total_weight += weight weights = NiceDict({c: total_weight for c in self.candidates_}) return {'gross_scores': gross_scores, 'weights': weights} @cached_property def gross_scores_(self) -> NiceDict: return self._gross_scores_and_weights_quicker_['gross_scores'] @cached_property def weights_(self) -> NiceDict: return self._gross_scores_and_weights_quicker_['weights']