sklearn.metrics
.make_scorer¶

sklearn.metrics.
make_scorer
(score_func, *, greater_is_better=True, needs_proba=False, needs_threshold=False, **kwargs)[source]¶ Make a scorer from a performance metric or loss function.
This factory function wraps scoring functions for use in
GridSearchCV
andcross_val_score
. It takes a score function, such asaccuracy_score
,mean_squared_error
,adjusted_rand_index
oraverage_precision
and returns a callable that scores an estimator’s output. The signature of the call is(estimator, X, y)
whereestimator
is the model to be evaluated,X
is the data andy
is the ground truth labeling (orNone
in the case of unsupervised models).Read more in the User Guide.
 Parameters
 score_funccallable
Score function (or loss function) with signature
score_func(y, y_pred, **kwargs)
. greater_is_betterbool, default=True
Whether score_func is a score function (default), meaning high is good, or a loss function, meaning low is good. In the latter case, the scorer object will signflip the outcome of the score_func.
 needs_probabool, default=False
Whether score_func requires predict_proba to get probability estimates out of a classifier.
If True, for binary
y_true
, the score function is supposed to accept a 1Dy_pred
(i.e., probability of the positive class, shape(n_samples,)
). needs_thresholdbool, default=False
Whether score_func takes a continuous decision certainty. This only works for binary classification using estimators that have either a decision_function or predict_proba method.
If True, for binary
y_true
, the score function is supposed to accept a 1Dy_pred
(i.e., probability of the positive class or the decision function, shape(n_samples,)
).For example
average_precision
or the area under the roc curve can not be computed using discrete predictions alone. **kwargsadditional arguments
Additional parameters to be passed to score_func.
 Returns
 scorercallable
Callable object that returns a scalar score; greater is better.
Notes
If
needs_proba=False
andneeds_threshold=False
, the score function is supposed to accept the output of predict. Ifneeds_proba=True
, the score function is supposed to accept the output of predict_proba (For binaryy_true
, the score function is supposed to accept probability of the positive class). Ifneeds_threshold=True
, the score function is supposed to accept the output of decision_function.Examples
>>> from sklearn.metrics import fbeta_score, make_scorer >>> ftwo_scorer = make_scorer(fbeta_score, beta=2) >>> ftwo_scorer make_scorer(fbeta_score, beta=2) >>> from sklearn.model_selection import GridSearchCV >>> from sklearn.svm import LinearSVC >>> grid = GridSearchCV(LinearSVC(), param_grid={'C': [1, 10]}, ... scoring=ftwo_scorer)