RuleBucklinByRounds¶

class whalrus.RuleBucklinByRounds(*args, converter: whalrus.converters_ballot.converter_ballot.ConverterBallot = None, scorer: whalrus.scorers.scorer_bucklin.ScorerBucklin = None, **kwargs)[source]¶

Bucklin’s rule (round by round version).

During the first round, a candidate’s score is the proportion of voters who rank it first. During the second round, its score is the proportion of voters who rank it first or second. Etc. More precisely, at each round, the scorer is used with k equal to the round number; cf. ScorerBucklin.

For another variant of Bucklin’s rule, cf. RuleBucklinInstant.

Parameters

args – Cf. parent class.
converter (ConverterBallot) – Default: ConverterBallotToOrder.
scorer (Scorer) – Default: ScorerBucklin.
kwargs – Cf. parent class.

Examples

>>> rule = RuleBucklinByRounds(['a > b > c > d', 'b > a > c > d',
...                             'c > a > b > d', 'd > a > b > c'])
>>> rule.detailed_scores_[0]
{'a': Fraction(1, 4), 'b': Fraction(1, 4), 'c': Fraction(1, 4), 'd': Fraction(1, 4)}
>>> rule.detailed_scores_[1]
{'a': 1, 'b': Fraction(1, 2), 'c': Fraction(1, 4), 'd': Fraction(1, 4)}
>>> rule.n_rounds_
2
>>> rule.scores_
{'a': 1, 'b': Fraction(1, 2), 'c': Fraction(1, 4), 'd': Fraction(1, 4)}
>>> rule.winner_
'a'

property average_score_¶

The average score.

Type: Number

property average_score_as_float_¶

The average score as a float. It is the same as average_score_, but converted to a float.

Type: float

property best_score_as_float_¶

The best score as a float. It is the same as RuleScore.best_score_, but converted to a float.

Type: float

compare_scores(one: numbers.Number, another: numbers.Number) → int¶

Compare two scores.

Parameters

one (object) – A score.
another (object) – A score.

Returns

0 if they are equal, a positive number if one is greater than another, a negative number otherwise.

Return type

int

property cotrailers_¶

“Cotrailers”. The set of candidates with the worst score.

Type: NiceSet

property cowinners_¶

Cowinners. The set of candidates with the best score.

Type: NiceSet

property detailed_scores_¶

Detailed scores. A list of NiceDict. The first dictionary gives the scores of the first round, etc.

Type: list

property detailed_scores_as_floats_¶

Detailed scores, as floats. It is the same as detailed_scores_, but converted to floats.

Examples

>>> rule = RuleBucklinByRounds(['a > b > c > d', 'b > a > c > d',
...                             'c > a > b > d', 'd > a > b > c'])
>>> rule.detailed_scores_as_floats_[0]
{'a': 0.25, 'b': 0.25, 'c': 0.25, 'd': 0.25}
>>> rule.detailed_scores_as_floats_[1]
{'a': 1.0, 'b': 0.5, 'c': 0.25, 'd': 0.25}

Type: list

property n_candidates_¶

Number of candidates.

Type: int

property n_rounds_¶

The number of rounds.

Type: int

property scores_¶

The scores. For each candidate, it gives its score during the final round, i.e. the first round where at least one candidate has a score above 1 / 2.

Type: NiceDict

property scores_as_floats_¶

Scores as floats. It is the same as scores_, but converted to floats.

Type: NiceDict

property strict_order_¶

Result of the election as a strict order over the candidates. The first element is the winner, etc. This may use the tie-breaking rule.

Type: list

property trailer_¶

The “trailer” of the election. This is the last candidate in strict_order_ and also the unfavorable choice of the tie-breaking rule in cotrailers_.

Type: object

property winner_¶

The winner of the election. This is the first candidate in strict_order_ and also the choice of the tie-breaking rule in cowinners_.

Type: object

property worst_score_as_float_¶

The worst score as a float. It is the same as RuleScore.worst_score_, but converted to a float.

Type: float