Note

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Release Highlights for scikit-learn 1.7

We are pleased to announce the release of scikit-learn 1.7! Many bug fixes and improvements were added, as well as some key new features. Below we detail the highlights of this release. For an exhaustive list of all the changes, please refer to the release notes.

To install the latest version (with pip):

pip install --upgrade scikit-learn

or with conda:

conda install -c conda-forge scikit-learn

Improved estimator’s HTML representation

The HTML representation of estimators now includes a section containing the list of parameters and their values. Non-default parameters are highlighted in orange. A copy button is also available to copy the “fully-qualified” parameter name without the need to call the get_params method. It is particularly useful when defining a parameter grid for a grid-search or a randomized-search with a complex pipeline.

See the example below and click on the different estimator’s blocks to see the improved HTML representation.

from sklearn.linear_model import LogisticRegression
from sklearn.pipeline import make_pipeline
from sklearn.preprocessing import StandardScaler

model = make_pipeline(StandardScaler(with_std=False), LogisticRegression(C=2.0))
model

Pipeline(steps=[('standardscaler', StandardScaler(with_std=False)),
                ('logisticregression', LogisticRegression(C=2.0))])

In a Jupyter environment, please rerun this cell to show the HTML representation or trust the notebook.
On GitHub, the HTML representation is unable to render, please try loading this page with nbviewer.org.

Custom validation set for histogram-based Gradient Boosting estimators

The ensemble.HistGradientBoostingClassifier and ensemble.HistGradientBoostingRegressor now support directly passing a custom validation set for early stopping to the fit method, using the X_val, y_val, and sample_weight_val parameters. In a pipeline.Pipeline, the validation set X_val can be transformed along with X using the transform_input parameter.

import sklearn
from sklearn.datasets import make_classification
from sklearn.ensemble import HistGradientBoostingClassifier
from sklearn.model_selection import train_test_split
from sklearn.pipeline import Pipeline
from sklearn.preprocessing import StandardScaler

sklearn.set_config(enable_metadata_routing=True)

X, y = make_classification(random_state=0)
X_train, X_val, y_train, y_val = train_test_split(X, y, test_size=0.2, random_state=0)

clf = HistGradientBoostingClassifier()
clf.set_fit_request(X_val=True, y_val=True)

model = Pipeline([("sc", StandardScaler()), ("clf", clf)], transform_input=["X_val"])
model.fit(X, y, X_val=X_val, y_val=y_val)

Pipeline(steps=[('sc', StandardScaler()),
                ('clf', HistGradientBoostingClassifier())],
         transform_input=['X_val'])

Pipeline

?Documentation for PipelineiFitted

Parameters

	steps steps: list of tuples List of (name of step, estimator) tuples that are to be chained in sequential order. To be compatible with the scikit-learn API, all steps must define `fit`. All non-last steps must also define `transform`. See :ref:`Combining Estimators <combining_estimators>` for more details.	[('sc', ...), ('clf', ...)]
	transform_input transform_input: list of str, default=None The names of the :term:`metadata` parameters that should be transformed by the pipeline before passing it to the step consuming it. This enables transforming some input arguments to ``fit`` (other than ``X``) to be transformed by the steps of the pipeline up to the step which requires them. Requirement is defined via :ref:`metadata routing <metadata_routing>`. For instance, this can be used to pass a validation set through the pipeline. You can only set this if metadata routing is enabled, which you can enable using ``sklearn.set_config(enable_metadata_routing=True)``. .. versionadded:: 1.6	['X_val']
	memory memory: str or object with the joblib.Memory interface, default=None Used to cache the fitted transformers of the pipeline. The last step will never be cached, even if it is a transformer. 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. See :ref:`sphx_glr_auto_examples_neighbors_plot_caching_nearest_neighbors.py` for an example on how to enable caching.	None
	verbose verbose: bool, default=False If True, the time elapsed while fitting each step will be printed as it is completed.	False

Fitted attributes

Name	Type	Value
classes_ classes_: ndarray of shape (n_classes,) The classes labels. Only exist if the last step of the pipeline is a classifier.	ndarray[int64](2,)	[0,1]
n_features_in_ n_features_in_: int Number of features seen during :term:`fit`. Only defined if the underlying first estimator in `steps` exposes such an attribute when fit. .. versionadded:: 0.24	int	20

StandardScaler

?Documentation for StandardScaler

Parameters

	copy copy: bool, default=True If False, try to avoid a copy and do inplace scaling instead. This is not guaranteed to always work inplace; e.g. if the data is not a NumPy array or scipy.sparse CSR matrix, a copy may still be returned.	True
	with_mean with_mean: bool, default=True If True, center the data before scaling. This does not work (and will raise an exception) when attempted on sparse matrices, because centering them entails building a dense matrix which in common use cases is likely to be too large to fit in memory.	True
	with_std with_std: bool, default=True If True, scale the data to unit variance (or equivalently, unit standard deviation).	True

Fitted attributes

Name	Type	Value
mean_ mean_: ndarray of shape (n_features,) or None The mean value for each feature in the training set. Equal to ``None`` when ``with_mean=False`` and ``with_std=False``.	ndarray[float64](20,)	[-0.2 ,-0.07,-0.02,...,-0.05, 0.22,-0.15]
n_features_in_ n_features_in_: int Number of features seen during :term:`fit`. .. versionadded:: 0.24	int	20
n_samples_seen_ n_samples_seen_: int or ndarray of shape (n_features,) The number of samples processed by the estimator for each feature. If there are no missing samples, the ``n_samples_seen`` will be an integer, otherwise it will be an array of dtype int. If `sample_weights` are used it will be a float (if no missing data) or an array of dtype float that sums the weights seen so far. Will be reset on new calls to fit, but increments across ``partial_fit`` calls.	float64	100
scale_ scale_: ndarray of shape (n_features,) or None Per feature relative scaling of the data to achieve zero mean and unit variance. Generally this is calculated using `np.sqrt(var_)`. If a variance is zero, we can't achieve unit variance, and the data is left as-is, giving a scaling factor of 1. `scale_` is equal to `None` when `with_std=False`. .. versionadded:: 0.17 scale_	ndarray[float64](20,)	[0.92,1.06,0.98,...,1.28,1.08,0.88]
var_ var_: ndarray of shape (n_features,) or None The variance for each feature in the training set. Used to compute `scale_`. Equal to ``None`` when ``with_mean=False`` and ``with_std=False``.	ndarray[float64](20,)	[0.84,1.13,0.96,...,1.65,1.17,0.77]

20 features

x10

x11

x12

x13

x14

x15

x16

x17

x18

x19

HistGradientBoostingClassifier

?Documentation for HistGradientBoostingClassifier

Parameters

	loss loss: {'log_loss'}, default='log_loss' The loss function to use in the boosting process. For binary classification problems, 'log_loss' is also known as logistic loss, binomial deviance or binary crossentropy. Internally, the model fits one tree per boosting iteration and uses the logistic sigmoid function (expit) as inverse link function to compute the predicted positive class probability. For multiclass classification problems, 'log_loss' is also known as multinomial deviance or categorical crossentropy. Internally, the model fits one tree per boosting iteration and per class and uses the softmax function as inverse link function to compute the predicted probabilities of the classes.	'log_loss'
	learning_rate learning_rate: float, default=0.1 The learning rate, also known as shrinkage. This is used as a multiplicative factor for the leaves values. Use ``1`` for no shrinkage.	0.1
	max_iter max_iter: int, default=100 The maximum number of iterations of the boosting process, i.e. the maximum number of trees for binary classification. For multiclass classification, `n_classes` trees per iteration are built.	100
	max_leaf_nodes max_leaf_nodes: int or None, default=31 The maximum number of leaves for each tree. Must be strictly greater than 1. If None, there is no maximum limit.	31
	max_depth max_depth: int or None, default=None The maximum depth of each tree. The depth of a tree is the number of edges to go from the root to the deepest leaf. Depth isn't constrained by default.	None
	min_samples_leaf min_samples_leaf: int, default=20 The minimum number of samples per leaf. For small datasets with less than a few hundred samples, it is recommended to lower this value since only very shallow trees would be built.	20
	l2_regularization l2_regularization: float, default=0 The L2 regularization parameter penalizing leaves with small hessians. Use ``0`` for no regularization (default).	0.0
	max_features max_features: float, default=1.0 Proportion of randomly chosen features in each and every node split. This is a form of regularization, smaller values make the trees weaker learners and might prevent overfitting. If interaction constraints from `interaction_cst` are present, only allowed features are taken into account for the subsampling. .. versionadded:: 1.4	1.0
	max_bins max_bins: int, default=255 The maximum number of bins to use for non-missing values. Before training, each feature of the input array `X` is binned into integer-valued bins, which allows for a much faster training stage. Features with a small number of unique values may use less than ``max_bins`` bins. In addition to the ``max_bins`` bins, one more bin is always reserved for missing values. Must be no larger than 255.	255
	categorical_features categorical_features: array-like of {bool, int, str} of shape (n_features) or shape (n_categorical_features,), default='from_dtype' Indicates the categorical features. - None : no feature will be considered categorical. - boolean array-like : boolean mask indicating categorical features. - integer array-like : integer indices indicating categorical features. - str array-like: names of categorical features (assuming the training data has feature names). - `"from_dtype"`: dataframe columns with dtype "Categorical" and "Enum" are considered to be categorical features. The input must be a dataframe that is supported by narwhals (or supports it): :func:`narwhals.from_native` must work. This is the case, for instance, for pandas and polars DataFrames. For each categorical feature, there must be at most `max_bins` unique categories. Negative values for categorical features encoded as numeric dtypes are treated as missing values. All categorical values are converted to floating point numbers. This means that categorical values of 1.0 and 1 are treated as the same category. Read more in the :ref:`User Guide <categorical_support_gbdt>`. .. versionadded:: 0.24 .. versionchanged:: 1.2 Added support for feature names. .. versionchanged:: 1.4 Added `"from_dtype"` option. .. versionchanged:: 1.6 The default value changed from `None` to `"from_dtype"`.	'from_dtype'
	monotonic_cst monotonic_cst: array-like of int of shape (n_features) or dict, default=None Monotonic constraint to enforce on each feature are specified using the following integer values: - 1: monotonic increase - 0: no constraint - -1: monotonic decrease If a dict with str keys, map feature to monotonic constraints by name. If an array, the features are mapped to constraints by position. See :ref:`monotonic_cst_features_names` for a usage example. The constraints are only valid for binary classifications and hold over the probability of the positive class. Read more in the :ref:`User Guide <monotonic_cst_gbdt>`. .. versionadded:: 0.23 .. versionchanged:: 1.2 Accept dict of constraints with feature names as keys.	None
	interaction_cst interaction_cst: {"pairwise", "no_interactions"} or sequence of lists/tuples/sets of int, default=None Specify interaction constraints, the sets of features which can interact with each other in child node splits. Each item specifies the set of feature indices that are allowed to interact with each other. If there are more features than specified in these constraints, they are treated as if they were specified as an additional set. The strings "pairwise" and "no_interactions" are shorthands for allowing only pairwise or no interactions, respectively. For instance, with 5 features in total, `interaction_cst=[{0, 1}]` is equivalent to `interaction_cst=[{0, 1}, {2, 3, 4}]`, and specifies that each branch of a tree will either only split on features 0 and 1 or only split on features 2, 3 and 4. See :ref:`this example<ice-vs-pdp>` on how to use `interaction_cst`. .. versionadded:: 1.2	None
	warm_start warm_start: bool, default=False When set to ``True``, reuse the solution of the previous call to fit and add more estimators to the ensemble. For results to be valid, the estimator should be re-trained on the same data only. See :term:`the Glossary <warm_start>`.	False
	early_stopping early_stopping: 'auto' or bool, default='auto' If 'auto', early stopping is enabled if the sample size is larger than 10000 or if `X_val` and `y_val` are passed to `fit`. If True, early stopping is enabled, otherwise early stopping is disabled. .. versionadded:: 0.23	'auto'
	scoring scoring: str or callable or None, default='loss' Scoring method to use for early stopping. Only used if `early_stopping` is enabled. Options: - str: see :ref:`scoring_string_names` for options. - callable: a scorer callable object (e.g., function) with signature ``scorer(estimator, X, y)``. See :ref:`scoring_callable` for details. - `None`: :ref:`accuracy <accuracy_score>` is used. - 'loss': early stopping is checked w.r.t the loss value.	'loss'
	validation_fraction validation_fraction: int or float or None, default=0.1 Proportion (or absolute size) of training data to set aside as validation data for early stopping. If None, early stopping is done on the training data. The value is ignored if either early stopping is not performed, e.g. `early_stopping=False`, or if `X_val` and `y_val` are passed to fit.	0.1
	n_iter_no_change n_iter_no_change: int, default=10 Used to determine when to "early stop". The fitting process is stopped when none of the last ``n_iter_no_change`` scores are better than the ``n_iter_no_change - 1`` -th-to-last one, up to some tolerance. Only used if early stopping is performed.	10
	tol tol: float, default=1e-7 The absolute tolerance to use when comparing scores. The higher the tolerance, the more likely we are to early stop: higher tolerance means that it will be harder for subsequent iterations to be considered an improvement upon the reference score.	1e-07
	verbose verbose: int, default=0 The verbosity level. If not zero, print some information about the fitting process. ``1`` prints only summary info, ``2`` prints info per iteration.	0
	random_state random_state: int, RandomState instance or None, default=None Pseudo-random number generator to control the subsampling in the binning process, and the train/validation data split if early stopping is enabled. Pass an int for reproducible output across multiple function calls. See :term:`Glossary <random_state>`.	None
	class_weight class_weight: dict or 'balanced', default=None Weights associated with classes in the form `{class_label: weight}`. If not given, all classes are supposed to have weight one. The "balanced" mode uses the values of y to automatically adjust weights inversely proportional to class frequencies in the input data as `n_samples / (n_classes * np.bincount(y))`. Note that these weights will be multiplied with sample_weight (passed through the fit method) if `sample_weight` is specified. .. versionadded:: 1.2	None

Fitted attributes

Name	Type	Value
classes_ classes_: array, shape = (n_classes,) Class labels.	ndarray[int64](2,)	[0,1]
do_early_stopping_ do_early_stopping_: bool Indicates whether early stopping is used during training.	bool	False
is_categorical_ is_categorical_: ndarray, shape (n_features, ) or None Boolean mask for the categorical features. ``None`` if there are no categorical features.	NoneType	None
n_features_in_ n_features_in_: int Number of features seen during :term:`fit`. .. versionadded:: 0.24	int	20
n_iter_ n_iter_: int The number of iterations as selected by early stopping, depending on the `early_stopping` parameter. Otherwise it corresponds to max_iter.	int	100
n_trees_per_iteration_ n_trees_per_iteration_: int The number of tree that are built at each iteration. This is equal to 1 for binary classification, and to ``n_classes`` for multiclass classification.	int	1
train_score_ train_score_: ndarray, shape (n_iter_+1,) The scores at each iteration on the training data. The first entry is the score of the ensemble before the first iteration. Scores are computed according to the ``scoring`` parameter. If ``scoring`` is not 'loss', scores are computed on a subset of at most 10 000 samples. Empty if no early stopping.	ndarray[float64](0,)	[]
validation_score_ validation_score_: ndarray, shape (n_iter_+1,) The scores at each iteration on the held-out validation data. The first entry is the score of the ensemble before the first iteration. Scores are computed according to the ``scoring`` parameter. Empty if no early stopping or if ``validation_fraction`` is None.	ndarray[float64](0,)	[]

Plotting ROC curves from cross-validation results

The class metrics.RocCurveDisplay has a new class method from_cv_results that allows to easily plot multiple ROC curves from the results of model_selection.cross_validate.

from sklearn.datasets import make_classification
from sklearn.linear_model import LogisticRegression
from sklearn.metrics import RocCurveDisplay
from sklearn.model_selection import cross_validate

X, y = make_classification(n_samples=150, random_state=0)
clf = LogisticRegression(random_state=0)
cv_results = cross_validate(clf, X, y, cv=5, return_estimator=True, return_indices=True)
_ = RocCurveDisplay.from_cv_results(cv_results, X, y)

Array API support

Several functions have been updated to support array API compatible inputs since version 1.6, especially metrics from the sklearn.metrics module.

In addition, it is no longer required to install the array-api-compat package to use the experimental array API support in scikit-learn.

Please refer to the array API support page for instructions to use scikit-learn with array API compatible libraries such as PyTorch or CuPy.

Improved API consistency of Multi-layer Perceptron

The neural_network.MLPRegressor has a new parameter loss and now supports the “poisson” loss in addition to the default “squared_error” loss. Moreover, the neural_network.MLPClassifier and neural_network.MLPRegressor estimators now support sample weights. These improvements have been made to improve the consistency of these estimators with regard to the other estimators in scikit-learn.

Migration toward sparse arrays

In order to prepare SciPy migration from sparse matrices to sparse arrays, all scikit-learn estimators that accept sparse matrices as input now also accept sparse arrays.

Total running time of the script: (0 minutes 0.154 seconds)

Related examples

Release Highlights for scikit-learn 1.6

Release Highlights for scikit-learn 1.2

Release Highlights for scikit-learn 0.23

Release Highlights for scikit-learn 0.22

© 2007–2026 The scikit-learn developers
Licensed under the 3-clause BSD License.
https://scikit-learn.org/1.9/auto_examples/release_highlights/plot_release_highlights_1_7_0.html

	C C: float, default=1.0 Inverse of regularization strength; must be a positive float. Like in support vector machines, smaller values specify stronger regularization. `C=np.inf` results in unpenalized logistic regression. For a visual example on the effect of tuning the `C` parameter with an L1 penalty, see: :ref:`sphx_glr_auto_examples_linear_model_plot_logistic_path.py`.	2.0
	penalty penalty: {'l1', 'l2', 'elasticnet', None}, default='l2' Specify the norm of the penalty: - `None`: no penalty is added; - `'l2'`: add an L2 penalty term and it is the default choice; - `'l1'`: add an L1 penalty term; - `'elasticnet'`: both L1 and L2 penalty terms are added. .. warning:: Some penalties may not work with some solvers. See the parameter `solver` below, to know the compatibility between the penalty and solver. .. versionadded:: 0.19 l1 penalty with SAGA solver (allowing 'multinomial' + L1) .. deprecated:: 1.8 `penalty` was deprecated in version 1.8 and will be removed in 1.10. Use `l1_ratio` and `C` instead. `l1_ratio=0` for `penalty='l2'`, `l1_ratio=1` for `penalty='l1'`, `l1_ratio` set to any float between 0 and 1 for `penalty='elasticnet'`, and `C=np.inf` for `penalty=None`.	'deprecated'
	l1_ratio l1_ratio: float, default=0.0 The Elastic-Net mixing parameter, with `0 <= l1_ratio <= 1`. Setting `l1_ratio=1` gives a pure L1-penalty, setting `l1_ratio=0` a pure L2-penalty. Any value between 0 and 1 gives an Elastic-Net penalty of the form `l1_ratio * L1 + (1 - l1_ratio) * L2`. .. warning:: Certain values of `l1_ratio`, i.e. some penalties, may not work with some solvers. See the parameter `solver` below, to know the compatibility between the penalty and solver. .. versionchanged:: 1.8 Default value changed from None to 0.0. .. deprecated:: 1.8 `None` is deprecated and will be removed in version 1.10. Always use `l1_ratio` to specify the penalty type.	0.0
	dual dual: bool, default=False Dual (constrained) or primal (regularized, see also :ref:`this equation <regularized-logistic-loss>`) formulation. Dual formulation is only implemented for l2 penalty with liblinear solver. Prefer `dual=False` when n_samples > n_features.	False
	tol tol: float, default=1e-4 Tolerance for stopping criteria.	0.0001
	fit_intercept fit_intercept: bool, default=True Specifies if a constant (a.k.a. bias or intercept) should be added to the decision function.	True
	intercept_scaling intercept_scaling: float, default=1 Useful only when the solver `liblinear` is used and `self.fit_intercept` is set to `True`. In this case, `x` becomes `[x, self.intercept_scaling]`, i.e. a "synthetic" feature with constant value equal to `intercept_scaling` is appended to the instance vector. The intercept becomes ``intercept_scaling * synthetic_feature_weight``. .. note:: The synthetic feature weight is subject to L1 or L2 regularization as all other features. To lessen the effect of regularization on synthetic feature weight (and therefore on the intercept) `intercept_scaling` has to be increased.	1
	class_weight class_weight: dict or 'balanced', default=None Weights associated with classes in the form ``{class_label: weight}``. If not given, all classes are supposed to have weight one. The "balanced" mode uses the values of y to automatically adjust weights inversely proportional to class frequencies in the input data as ``n_samples / (n_classes * np.bincount(y))``. Note that these weights will be multiplied with sample_weight (passed through the fit method) if sample_weight is specified. .. versionadded:: 0.17 class_weight='balanced'	None
	random_state random_state: int, RandomState instance, default=None Used when ``solver`` == 'sag', 'saga' or 'liblinear' to shuffle the data. See :term:`Glossary <random_state>` for details.	None
	solver solver: {'lbfgs', 'liblinear', 'newton-cg', 'newton-cholesky', 'sag', 'saga'}, default='lbfgs' Algorithm to use in the optimization problem. Default is 'lbfgs'. To choose a solver, you might want to consider the following aspects: - 'lbfgs' is a good default solver because it works reasonably well for a wide class of problems. - For :term:`multiclass` problems (`n_classes >= 3`), all solvers except 'liblinear' minimize the full multinomial loss, 'liblinear' will raise an error. - 'newton-cholesky' is a good choice for `n_samples` >> `n_features * n_classes`, especially with one-hot encoded categorical features with rare categories. Be aware that the memory usage of this solver has a quadratic dependency on `n_features * n_classes` because it explicitly computes the full Hessian matrix. - For small datasets, 'liblinear' is a good choice, whereas 'sag' and 'saga' are faster for large ones; - 'liblinear' can only handle binary classification by default. To apply a one-versus-rest scheme for the multiclass setting one can wrap it with the :class:`~sklearn.multiclass.OneVsRestClassifier`. .. warning:: The choice of the algorithm depends on the penalty chosen (`l1_ratio=0` for L2-penalty, `l1_ratio=1` for L1-penalty and `0 < l1_ratio < 1` for Elastic-Net) and on (multinomial) multiclass support: ================= ======================== ====================== solver l1_ratio multinomial multiclass ================= ======================== ====================== 'lbfgs' l1_ratio=0 yes 'liblinear' l1_ratio=1 or l1_ratio=0 no 'newton-cg' l1_ratio=0 yes 'newton-cholesky' l1_ratio=0 yes 'sag' l1_ratio=0 yes 'saga' 0<=l1_ratio<=1 yes ================= ======================== ====================== .. note:: 'sag' and 'saga' fast convergence is only guaranteed on features with approximately the same scale. You can preprocess the data with a scaler from :mod:`sklearn.preprocessing`. .. seealso:: Refer to the :ref:`User Guide <Logistic_regression>` for more information regarding :class:`LogisticRegression` and more specifically the :ref:`Table <logistic_regression_solvers>` summarizing solver/penalty supports. .. versionadded:: 0.17 Stochastic Average Gradient (SAG) descent solver. Multinomial support in version 0.18. .. versionadded:: 0.19 SAGA solver. .. versionchanged:: 0.22 The default solver changed from 'liblinear' to 'lbfgs' in 0.22. .. versionadded:: 1.2 newton-cholesky solver. Multinomial support in version 1.6.	'lbfgs'
	max_iter max_iter: int, default=100 Maximum number of iterations taken for the solvers to converge.	100
	verbose verbose: int, default=0 For the liblinear and lbfgs solvers set verbose to any positive number for verbosity.	0
	warm_start warm_start: bool, default=False When set to True, reuse the solution of the previous call to fit as initialization, otherwise, just erase the previous solution. Useless for liblinear solver. See :term:`the Glossary <warm_start>`. .. versionadded:: 0.17 warm_start to support lbfgs, newton-cg, sag, saga solvers.	False
	n_jobs n_jobs: int, default=None Does not have any effect. .. deprecated:: 1.8 `n_jobs` is deprecated in version 1.8 and will be removed in 1.10.	None

	steps steps: list of tuples List of (name of step, estimator) tuples that are to be chained in sequential order. To be compatible with the scikit-learn API, all steps must define `fit`. All non-last steps must also define `transform`. See :ref:`Combining Estimators <combining_estimators>` for more details.	[('standardscaler', ...), ('logisticregression', ...)]
	transform_input transform_input: list of str, default=None The names of the :term:`metadata` parameters that should be transformed by the pipeline before passing it to the step consuming it. This enables transforming some input arguments to ``fit`` (other than ``X``) to be transformed by the steps of the pipeline up to the step which requires them. Requirement is defined via :ref:`metadata routing <metadata_routing>`. For instance, this can be used to pass a validation set through the pipeline. You can only set this if metadata routing is enabled, which you can enable using ``sklearn.set_config(enable_metadata_routing=True)``. .. versionadded:: 1.6	None
	memory memory: str or object with the joblib.Memory interface, default=None Used to cache the fitted transformers of the pipeline. The last step will never be cached, even if it is a transformer. 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. See :ref:`sphx_glr_auto_examples_neighbors_plot_caching_nearest_neighbors.py` for an example on how to enable caching.	None
	verbose verbose: bool, default=False If True, the time elapsed while fitting each step will be printed as it is completed.	False