sklearn.pipeline
.Pipeline¶

class
sklearn.pipeline.
Pipeline
(steps, memory=None)[source]¶ Pipeline of transforms with a final estimator.
Sequentially apply a list of transforms and a final estimator. Intermediate steps of the pipeline must be ‘transforms’, that is, they must implement fit and transform methods. The final estimator only needs to implement fit. The transformers in the pipeline can be cached using
memory
argument.The purpose of the pipeline is to assemble several steps that can be crossvalidated together while setting different parameters. For this, it enables setting parameters of the various steps using their names and the parameter name separated by a ‘__’, as in the example below. A step’s estimator may be replaced entirely by setting the parameter with its name to another estimator, or a transformer removed by setting it to ‘passthrough’ or
None
.Read more in the User Guide.
Parameters:  steps : list
List of (name, transform) tuples (implementing fit/transform) that are chained, in the order in which they are chained, with the last object an estimator.
 memory : None, str or object with the joblib.Memory interface, optional
Used to cache the fitted transformers of the pipeline. By default, no caching is performed. If a string is given, it is the path to the caching directory. Enabling caching triggers a clone of the transformers before fitting. Therefore, the transformer instance given to the pipeline cannot be inspected directly. Use the attribute
named_steps
orsteps
to inspect estimators within the pipeline. Caching the transformers is advantageous when fitting is time consuming.
Attributes:  named_steps : bunch object, a dictionary with attribute access
Readonly attribute to access any step parameter by user given name. Keys are step names and values are steps parameters.
See also
sklearn.pipeline.make_pipeline
 convenience function for simplified pipeline construction.
Examples
>>> from sklearn import svm >>> from sklearn.datasets import samples_generator >>> from sklearn.feature_selection import SelectKBest >>> from sklearn.feature_selection import f_regression >>> from sklearn.pipeline import Pipeline >>> # generate some data to play with >>> X, y = samples_generator.make_classification( ... n_informative=5, n_redundant=0, random_state=42) >>> # ANOVA SVMC >>> anova_filter = SelectKBest(f_regression, k=5) >>> clf = svm.SVC(kernel='linear') >>> anova_svm = Pipeline([('anova', anova_filter), ('svc', clf)]) >>> # You can set the parameters using the names issued >>> # For instance, fit using a k of 10 in the SelectKBest >>> # and a parameter 'C' of the svm >>> anova_svm.set_params(anova__k=10, svc__C=.1).fit(X, y) ... Pipeline(memory=None, steps=[('anova', SelectKBest(...)), ('svc', SVC(...))]) >>> prediction = anova_svm.predict(X) >>> anova_svm.score(X, y) 0.83 >>> # getting the selected features chosen by anova_filter >>> anova_svm['anova'].get_support() ... array([False, False, True, True, False, False, True, True, False, True, False, True, True, False, True, False, True, True, False, False]) >>> # Another way to get selected features chosen by anova_filter >>> anova_svm.named_steps.anova.get_support() ... array([False, False, True, True, False, False, True, True, False, True, False, True, True, False, True, False, True, True, False, False]) >>> # Indexing can also be used to extract a subpipeline. >>> sub_pipeline = anova_svm[:1] >>> sub_pipeline Pipeline(memory=None, steps=[('anova', ...)]) >>> coef = anova_svm[1].coef_ >>> anova_svm['svc'] is anova_svm[1] True >>> coef.shape (1, 10) >>> sub_pipeline.inverse_transform(coef).shape (1, 20)
Methods
decision_function
(X)Apply transforms, and decision_function of the final estimator fit
(X[, y])Fit the model fit_predict
(X[, y])Applies fit_predict of last step in pipeline after transforms. fit_transform
(X[, y])Fit the model and transform with the final estimator get_params
([deep])Get parameters for this estimator. predict
(X, **predict_params)Apply transforms to the data, and predict with the final estimator predict_log_proba
(X)Apply transforms, and predict_log_proba of the final estimator predict_proba
(X)Apply transforms, and predict_proba of the final estimator score
(X[, y, sample_weight])Apply transforms, and score with the final estimator set_params
(**kwargs)Set the parameters of this estimator. 
decision_function
(X)[source]¶ Apply transforms, and decision_function of the final estimator
Parameters:  X : iterable
Data to predict on. Must fulfill input requirements of first step of the pipeline.
Returns:  y_score : arraylike, shape = [n_samples, n_classes]

fit
(X, y=None, **fit_params)[source]¶ Fit the model
Fit all the transforms one after the other and transform the data, then fit the transformed data using the final estimator.
Parameters:  X : iterable
Training data. Must fulfill input requirements of first step of the pipeline.
 y : iterable, default=None
Training targets. Must fulfill label requirements for all steps of the pipeline.
 **fit_params : dict of string > object
Parameters passed to the
fit
method of each step, where each parameter name is prefixed such that parameterp
for steps
has keys__p
.
Returns:  self : Pipeline
This estimator

fit_predict
(X, y=None, **fit_params)[source]¶ Applies fit_predict of last step in pipeline after transforms.
Applies fit_transforms of a pipeline to the data, followed by the fit_predict method of the final estimator in the pipeline. Valid only if the final estimator implements fit_predict.
Parameters:  X : iterable
Training data. Must fulfill input requirements of first step of the pipeline.
 y : iterable, default=None
Training targets. Must fulfill label requirements for all steps of the pipeline.
 **fit_params : dict of string > object
Parameters passed to the
fit
method of each step, where each parameter name is prefixed such that parameterp
for steps
has keys__p
.
Returns:  y_pred : arraylike

fit_transform
(X, y=None, **fit_params)[source]¶ Fit the model and transform with the final estimator
Fits all the transforms one after the other and transforms the data, then uses fit_transform on transformed data with the final estimator.
Parameters:  X : iterable
Training data. Must fulfill input requirements of first step of the pipeline.
 y : iterable, default=None
Training targets. Must fulfill label requirements for all steps of the pipeline.
 **fit_params : dict of string > object
Parameters passed to the
fit
method of each step, where each parameter name is prefixed such that parameterp
for steps
has keys__p
.
Returns:  Xt : arraylike, shape = [n_samples, n_transformed_features]
Transformed samples

get_params
(deep=True)[source]¶ Get parameters for this estimator.
Parameters:  deep : boolean, optional
If True, will return the parameters for this estimator and contained subobjects that are estimators.
Returns:  params : mapping of string to any
Parameter names mapped to their values.

inverse_transform
¶ Apply inverse transformations in reverse order
All estimators in the pipeline must support
inverse_transform
.Parameters:  Xt : arraylike, shape = [n_samples, n_transformed_features]
Data samples, where
n_samples
is the number of samples andn_features
is the number of features. Must fulfill input requirements of last step of pipeline’sinverse_transform
method.
Returns:  Xt : arraylike, shape = [n_samples, n_features]

predict
(X, **predict_params)[source]¶ Apply transforms to the data, and predict with the final estimator
Parameters:  X : iterable
Data to predict on. Must fulfill input requirements of first step of the pipeline.
 **predict_params : dict of string > object
Parameters to the
predict
called at the end of all transformations in the pipeline. Note that while this may be used to return uncertainties from some models with return_std or return_cov, uncertainties that are generated by the transformations in the pipeline are not propagated to the final estimator.
Returns:  y_pred : arraylike

predict_log_proba
(X)[source]¶ Apply transforms, and predict_log_proba of the final estimator
Parameters:  X : iterable
Data to predict on. Must fulfill input requirements of first step of the pipeline.
Returns:  y_score : arraylike, shape = [n_samples, n_classes]

predict_proba
(X)[source]¶ Apply transforms, and predict_proba of the final estimator
Parameters:  X : iterable
Data to predict on. Must fulfill input requirements of first step of the pipeline.
Returns:  y_proba : arraylike, shape = [n_samples, n_classes]

score
(X, y=None, sample_weight=None)[source]¶ Apply transforms, and score with the final estimator
Parameters:  X : iterable
Data to predict on. Must fulfill input requirements of first step of the pipeline.
 y : iterable, default=None
Targets used for scoring. Must fulfill label requirements for all steps of the pipeline.
 sample_weight : arraylike, default=None
If not None, this argument is passed as
sample_weight
keyword argument to thescore
method of the final estimator.
Returns:  score : float

set_params
(**kwargs)[source]¶ Set the parameters of this estimator.
Valid parameter keys can be listed with
get_params()
.Returns:  self

transform
¶ Apply transforms, and transform with the final estimator
This also works where final estimator is
None
: all prior transformations are applied.Parameters:  X : iterable
Data to transform. Must fulfill input requirements of first step of the pipeline.
Returns:  Xt : arraylike, shape = [n_samples, n_transformed_features]