imblearn.pipeline.Pipeline

class imblearn.pipeline.Pipeline(steps, *, memory=None, verbose=False)[source]

Pipeline of transforms and resamples with a final estimator.

Sequentially apply a list of transforms, sampling, and a final estimator. Intermediate steps of the pipeline must be transformers or resamplers, that is, they must implement fit, transform and sample methods. The samplers are only applied during fit. The final estimator only needs to implement fit. The transformers and samplers in the pipeline can be cached using memory argument.

The purpose of the pipeline is to assemble several steps that can be cross-validated 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.

Parameters
stepslist

List of (name, transform) tuples (implementing fit/transform/fit_resample) that are chained, in the order in which they are chained, with the last object an estimator.

memoryInstance of joblib.Memory or str, default=None

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 or steps to inspect estimators within the pipeline. Caching the transformers is advantageous when fitting is time consuming.

verbosebool, default=False

If True, the time elapsed while fitting each step will be printed as it is completed.

See also

make_pipeline

Helper function to make pipeline.

Notes

See Pipeline Object

Examples

>>> from collections import Counter
>>> from sklearn.datasets import make_classification
>>> from sklearn.model_selection import train_test_split as tts
>>> from sklearn.decomposition import PCA
>>> from sklearn.neighbors import KNeighborsClassifier as KNN
>>> from sklearn.metrics import classification_report
>>> from imblearn.over_sampling import SMOTE
>>> from imblearn.pipeline import Pipeline 
>>> X, y = make_classification(n_classes=2, class_sep=2,
... weights=[0.1, 0.9], n_informative=3, n_redundant=1, flip_y=0,
... n_features=20, n_clusters_per_class=1, n_samples=1000, random_state=10)
>>> print('Original dataset shape {}'.format(Counter(y)))
Original dataset shape Counter({1: 900, 0: 100})
>>> pca = PCA()
>>> smt = SMOTE(random_state=42)
>>> knn = KNN()
>>> pipeline = Pipeline([('smt', smt), ('pca', pca), ('knn', knn)])
>>> X_train, X_test, y_train, y_test = tts(X, y, random_state=42)
>>> pipeline.fit(X_train, y_train) 
Pipeline(...)
>>> y_hat = pipeline.predict(X_test)
>>> print(classification_report(y_test, y_hat))
              precision    recall  f1-score   support

           0       0.87      1.00      0.93        26
           1       1.00      0.98      0.99       224

    accuracy                           0.98       250
   macro avg       0.93      0.99      0.96       250
weighted avg       0.99      0.98      0.98       250
Attributes
named_stepsbunch object, a dictionary with attribute access

Read-only attribute to access any step parameter by user given name. Keys are step names and values are steps parameters.

__init__(self, steps, *, memory=None, verbose=False)[source]

Initialize self. See help(type(self)) for accurate signature.