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}

average_score_¶

The average score.

Type:	Number

average_score_as_float_¶

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

Type:	float

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

cotrailers_¶

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

Type:	NiceSet

cowinners_¶

Cowinners. The set of candidates with the best score.

Type:	NiceSet

matrix_¶

The matrix (once computed with the given profile).

Type:	Matrix

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

n_candidates_¶

Number of candidates.

Type:	int

scores_as_floats_¶

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

Type:	NiceDict

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

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

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

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