RuleCopeland¶

class whalrus.RuleCopeland(*args, converter: whalrus.converters_ballot.converter_ballot.ConverterBallot = None, matrix: whalrus.matrices.matrix.Matrix = None, **kwargs)[source]¶

Copeland’s rule.

Parameters

args – Cf. parent class.
converter (ConverterBallot) – Default: ConverterBallotToOrder.
matrix (Matrix) – Default: MatrixMajority.
kwargs – Cf. parent class.

Examples

The score of a candidate is the number of victories in the majority matrix.

>>> rule = RuleCopeland(ballots=['a > b > c', 'b > a > c', 'c > a > b'])
>>> rule.matrix_.as_array_
array([[Fraction(1, 2), 1, 1],
       [0, Fraction(1, 2), 1],
       [0, 0, Fraction(1, 2)]], dtype=object)
>>> rule.scores_
{'a': 2, 'b': 1, 'c': 0}

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 matrix_¶

The matrix (once computed with the given profile).

Type: Matrix

property matrix_majority_¶

The majority matrix. This is an alias for matrix_.

Examples

>>> rule = RuleCopeland(ballots=['a > b > c', 'b > a > c', 'c > a > b'])
>>> rule.matrix_majority_.as_array_
array([[Fraction(1, 2), 1, 1],
       [0, Fraction(1, 2), 1],
       [0, 0, Fraction(1, 2)]], dtype=object)

Type: Matrix

property n_candidates_¶

Number of candidates.

Type: int

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