Source code for whalrus.eliminations.elimination_below_average

# -*- 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/>.
"""
from whalrus.utils.utils import cached_property
from whalrus.rules.rule_score_num import RuleScoreNum
from whalrus.eliminations.elimination import Elimination
from whalrus.rules.rule_plurality import RulePlurality


[docs]class EliminationBelowAverage(Elimination): """ Elimination of the candidates whose score is lower than the average score Parameters ---------- args Cf. parent class. strict : bool If True (resp. False), then eliminate the candidates whose score is strictly lower than (resp. lower or equal to) the average. kwargs Cf. parent class. Examples -------- >>> rule = RulePlurality(ballots=['a', 'b', 'c', 'd'], weights=[35, 30, 25, 10]) >>> rule.gross_scores_ {'a': 35, 'b': 30, 'c': 25, 'd': 10} >>> EliminationBelowAverage(rule=rule).eliminated_ {'d'} >>> EliminationBelowAverage(rule=rule, strict=False).eliminated_ {'c', 'd'} If no candidates should be eliminated (which may happen only if ``strict`` is True), then all candidates are eliminated. >>> rule = RulePlurality(ballots=['a', 'b']) >>> rule.gross_scores_ {'a': 1, 'b': 1} >>> EliminationBelowAverage(rule=rule).eliminated_ {'a', 'b'} """ def __init__(self, *args, strict=True, **kwargs): self.strict = strict super().__init__(*args, **kwargs) def __call__(self, rule: RuleScoreNum): return super().__call__(rule=rule) @cached_property def eliminated_order_(self): if self.rule_.best_score_ == self.rule_.worst_score_: return self.rule_.order_ worst_first = [] for tie_class in self.rule_.order_[::-1]: some_candidate = list(tie_class)[0] score = self.rule_.scores_[some_candidate] if score < self.rule_.average_score_ or (not self.strict and score == self.rule_.average_score_): worst_first.append(tie_class) else: break return worst_first[::-1]