"""
The :mod:`sklearn.pipeline` module implements utilities to build a composite
estimator, as a chain of transforms and estimators.
"""
# Author: Edouard Duchesnay
# Gael Varoquaux
# Virgile Fritsch
# Alexandre Gramfort
# Lars Buitinck
# License: BSD
from collections import defaultdict
from itertools import islice
import numpy as np
from scipy import sparse
from joblib import Parallel
from .base import clone, TransformerMixin
from .preprocessing import FunctionTransformer
from .utils._estimator_html_repr import _VisualBlock
from .utils.metaestimators import available_if
from .utils import (
Bunch,
_print_elapsed_time,
)
from .utils.deprecation import deprecated
from .utils._tags import _safe_tags
from .utils.validation import check_memory
from .utils.validation import check_is_fitted
from .utils.fixes import delayed
from .exceptions import NotFittedError
from .utils.metaestimators import _BaseComposition
__all__ = ["Pipeline", "FeatureUnion", "make_pipeline", "make_union"]
def _final_estimator_has(attr):
"""Check that final_estimator has `attr`.
Used together with `avaliable_if` in `Pipeline`."""
def check(self):
# raise original `AttributeError` if `attr` does not exist
getattr(self._final_estimator, attr)
return True
return check
class Pipeline(_BaseComposition):
"""
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
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`.
Read more in the :ref:`User Guide <pipeline>`.
.. versionadded:: 0.5
Parameters
----------
steps : list of tuple
List of (name, transform) tuples (implementing `fit`/`transform`) that
are chained in sequential order. The last transform must be an
estimator.
memory : str or object with the joblib.Memory interface, 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.
verbose : bool, default=False
If True, the time elapsed while fitting each step will be printed as it
is completed.
Attributes
----------
named_steps : :class:`~sklearn.utils.Bunch`
Dictionary-like object, with the following attributes.
Read-only attribute to access any step parameter by user given name.
Keys are step names and values are steps parameters.
classes_ : ndarray of shape (n_classes,)
The classes labels. Only exist if the last step of the pipeline is a
classifier.
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
feature_names_in_ : ndarray of shape (`n_features_in_`,)
Names of features seen during :term:`fit`. Only defined if the
underlying estimator exposes such an attribute when fit.
.. versionadded:: 1.0
See Also
--------
make_pipeline : Convenience function for simplified pipeline construction.
Examples
--------
>>> from sklearn.svm import SVC
>>> from sklearn.preprocessing import StandardScaler
>>> from sklearn.datasets import make_classification
>>> from sklearn.model_selection import train_test_split
>>> from sklearn.pipeline import Pipeline
>>> X, y = make_classification(random_state=0)
>>> X_train, X_test, y_train, y_test = train_test_split(X, y,
... random_state=0)
>>> pipe = Pipeline([('scaler', StandardScaler()), ('svc', SVC())])
>>> # The pipeline can be used as any other estimator
>>> # and avoids leaking the test set into the train set
>>> pipe.fit(X_train, y_train)
Pipeline(steps=[('scaler', StandardScaler()), ('svc', SVC())])
>>> pipe.score(X_test, y_test)
0.88
"""
# BaseEstimator interface
_required_parameters = ["steps"]
def __init__(self, steps, *, memory=None, verbose=False):
self.steps = steps
self.memory = memory
self.verbose = verbose
[docs] def get_params(self, deep=True):
"""Get parameters for this estimator.
Returns the parameters given in the constructor as well as the
estimators contained within the `steps` of the `Pipeline`.
Parameters
----------
deep : bool, default=True
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.
"""
return self._get_params("steps", deep=deep)
[docs] def set_params(self, **kwargs):
"""Set the parameters of this estimator.
Valid parameter keys can be listed with ``get_params()``. Note that
you can directly set the parameters of the estimators contained in
`steps`.
Parameters
----------
**kwargs : dict
Parameters of this estimator or parameters of estimators contained
in `steps`. Parameters of the steps may be set using its name and
the parameter name separated by a '__'.
Returns
-------
self : object
Pipeline class instance.
"""
self._set_params("steps", **kwargs)
return self
def _validate_steps(self):
names, estimators = zip(*self.steps)
# validate names
self._validate_names(names)
# validate estimators
transformers = estimators[:-1]
estimator = estimators[-1]
for t in transformers:
if t is None or t == "passthrough":
continue
if not (hasattr(t, "fit") or hasattr(t, "fit_transform")) or not hasattr(
t, "transform"
):
raise TypeError(
"All intermediate steps should be "
"transformers and implement fit and transform "
"or be the string 'passthrough' "
"'%s' (type %s) doesn't" % (t, type(t))
)
# We allow last estimator to be None as an identity transformation
if (
estimator is not None
and estimator != "passthrough"
and not hasattr(estimator, "fit")
):
raise TypeError(
"Last step of Pipeline should implement fit "
"or be the string 'passthrough'. "
"'%s' (type %s) doesn't" % (estimator, type(estimator))
)
def _iter(self, with_final=True, filter_passthrough=True):
"""
Generate (idx, (name, trans)) tuples from self.steps
When filter_passthrough is True, 'passthrough' and None transformers
are filtered out.
"""
stop = len(self.steps)
if not with_final:
stop -= 1
for idx, (name, trans) in enumerate(islice(self.steps, 0, stop)):
if not filter_passthrough:
yield idx, name, trans
elif trans is not None and trans != "passthrough":
yield idx, name, trans
def __len__(self):
"""
Returns the length of the Pipeline
"""
return len(self.steps)
def __getitem__(self, ind):
"""Returns a sub-pipeline or a single estimator in the pipeline
Indexing with an integer will return an estimator; using a slice
returns another Pipeline instance which copies a slice of this
Pipeline. This copy is shallow: modifying (or fitting) estimators in
the sub-pipeline will affect the larger pipeline and vice-versa.
However, replacing a value in `step` will not affect a copy.
"""
if isinstance(ind, slice):
if ind.step not in (1, None):
raise ValueError("Pipeline slicing only supports a step of 1")
return self.__class__(
self.steps[ind], memory=self.memory, verbose=self.verbose
)
try:
name, est = self.steps[ind]
except TypeError:
# Not an int, try get step by name
return self.named_steps[ind]
return est
@property
def _estimator_type(self):
return self.steps[-1][1]._estimator_type
@property
def named_steps(self):
"""Access the steps by name.
Read-only attribute to access any step by given name.
Keys are steps names and values are the steps objects."""
# Use Bunch object to improve autocomplete
return Bunch(**dict(self.steps))
@property
def _final_estimator(self):
estimator = self.steps[-1][1]
return "passthrough" if estimator is None else estimator
def _log_message(self, step_idx):
if not self.verbose:
return None
name, _ = self.steps[step_idx]
return "(step %d of %d) Processing %s" % (step_idx + 1, len(self.steps), name)
def _check_fit_params(self, **fit_params):
fit_params_steps = {name: {} for name, step in self.steps if step is not None}
for pname, pval in fit_params.items():
if "__" not in pname:
raise ValueError(
"Pipeline.fit does not accept the {} parameter. "
"You can pass parameters to specific steps of your "
"pipeline using the stepname__parameter format, e.g. "
"`Pipeline.fit(X, y, logisticregression__sample_weight"
"=sample_weight)`.".format(pname)
)
step, param = pname.split("__", 1)
fit_params_steps[step][param] = pval
return fit_params_steps
# Estimator interface
def _fit(self, X, y=None, **fit_params_steps):
# shallow copy of steps - this should really be steps_
self.steps = list(self.steps)
self._validate_steps()
# Setup the memory
memory = check_memory(self.memory)
fit_transform_one_cached = memory.cache(_fit_transform_one)
for step_idx, name, transformer in self._iter(
with_final=False, filter_passthrough=False
):
if transformer is None or transformer == "passthrough":
with _print_elapsed_time("Pipeline", self._log_message(step_idx)):
continue
if hasattr(memory, "location") and memory.location is None:
# we do not clone when caching is disabled to
# preserve backward compatibility
cloned_transformer = transformer
else:
cloned_transformer = clone(transformer)
# Fit or load from cache the current transformer
X, fitted_transformer = fit_transform_one_cached(
cloned_transformer,
X,
y,
None,
message_clsname="Pipeline",
message=self._log_message(step_idx),
**fit_params_steps[name],
)
# Replace the transformer of the step with the fitted
# transformer. This is necessary when loading the transformer
# from the cache.
self.steps[step_idx] = (name, fitted_transformer)
return X
[docs] def fit(self, X, y=None, **fit_params):
"""Fit the model.
Fit all the transformers one after the other and transform the
data. Finally, 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 parameter ``p`` for step
``s`` has key ``s__p``.
Returns
-------
self : object
Pipeline with fitted steps.
"""
fit_params_steps = self._check_fit_params(**fit_params)
Xt = self._fit(X, y, **fit_params_steps)
with _print_elapsed_time("Pipeline", self._log_message(len(self.steps) - 1)):
if self._final_estimator != "passthrough":
fit_params_last_step = fit_params_steps[self.steps[-1][0]]
self._final_estimator.fit(Xt, y, **fit_params_last_step)
return self
[docs] @available_if(_final_estimator_has("predict"))
def predict(self, X, **predict_params):
"""Transform the data, and apply `predict` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls `predict`
method. Only valid if the final estimator implements `predict`.
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.
.. versionadded:: 0.20
Returns
-------
y_pred : ndarray
Result of calling `predict` on the final estimator.
"""
Xt = X
for _, name, transform in self._iter(with_final=False):
Xt = transform.transform(Xt)
return self.steps[-1][1].predict(Xt, **predict_params)
[docs] @available_if(_final_estimator_has("fit_predict"))
def fit_predict(self, X, y=None, **fit_params):
"""Transform the data, and apply `fit_predict` with the final estimator.
Call `fit_transform` of each transformer in the pipeline. The
transformed data are finally passed to the final estimator that calls
`fit_predict` method. Only valid 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 parameter ``p`` for step
``s`` has key ``s__p``.
Returns
-------
y_pred : ndarray
Result of calling `fit_predict` on the final estimator.
"""
fit_params_steps = self._check_fit_params(**fit_params)
Xt = self._fit(X, y, **fit_params_steps)
fit_params_last_step = fit_params_steps[self.steps[-1][0]]
with _print_elapsed_time("Pipeline", self._log_message(len(self.steps) - 1)):
y_pred = self.steps[-1][1].fit_predict(Xt, y, **fit_params_last_step)
return y_pred
[docs] @available_if(_final_estimator_has("predict_proba"))
def predict_proba(self, X, **predict_proba_params):
"""Transform the data, and apply `predict_proba` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls
`predict_proba` method. Only valid if the final estimator implements
`predict_proba`.
Parameters
----------
X : iterable
Data to predict on. Must fulfill input requirements of first step
of the pipeline.
**predict_proba_params : dict of string -> object
Parameters to the `predict_proba` called at the end of all
transformations in the pipeline.
Returns
-------
y_proba : ndarray of shape (n_samples, n_classes)
Result of calling `predict_proba` on the final estimator.
"""
Xt = X
for _, name, transform in self._iter(with_final=False):
Xt = transform.transform(Xt)
return self.steps[-1][1].predict_proba(Xt, **predict_proba_params)
[docs] @available_if(_final_estimator_has("decision_function"))
def decision_function(self, X):
"""Transform the data, and apply `decision_function` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls
`decision_function` method. Only valid if the final estimator
implements `decision_function`.
Parameters
----------
X : iterable
Data to predict on. Must fulfill input requirements of first step
of the pipeline.
Returns
-------
y_score : ndarray of shape (n_samples, n_classes)
Result of calling `decision_function` on the final estimator.
"""
Xt = X
for _, name, transform in self._iter(with_final=False):
Xt = transform.transform(Xt)
return self.steps[-1][1].decision_function(Xt)
[docs] @available_if(_final_estimator_has("score_samples"))
def score_samples(self, X):
"""Transform the data, and apply `score_samples` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls
`score_samples` method. Only valid if the final estimator implements
`score_samples`.
Parameters
----------
X : iterable
Data to predict on. Must fulfill input requirements of first step
of the pipeline.
Returns
-------
y_score : ndarray of shape (n_samples,)
Result of calling `score_samples` on the final estimator.
"""
Xt = X
for _, _, transformer in self._iter(with_final=False):
Xt = transformer.transform(Xt)
return self.steps[-1][1].score_samples(Xt)
[docs] @available_if(_final_estimator_has("predict_log_proba"))
def predict_log_proba(self, X, **predict_log_proba_params):
"""Transform the data, and apply `predict_log_proba` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls
`predict_log_proba` method. Only valid if the final estimator
implements `predict_log_proba`.
Parameters
----------
X : iterable
Data to predict on. Must fulfill input requirements of first step
of the pipeline.
**predict_log_proba_params : dict of string -> object
Parameters to the ``predict_log_proba`` called at the end of all
transformations in the pipeline.
Returns
-------
y_log_proba : ndarray of shape (n_samples, n_classes)
Result of calling `predict_log_proba` on the final estimator.
"""
Xt = X
for _, name, transform in self._iter(with_final=False):
Xt = transform.transform(Xt)
return self.steps[-1][1].predict_log_proba(Xt, **predict_log_proba_params)
def _can_transform(self):
return self._final_estimator == "passthrough" or hasattr(
self._final_estimator, "transform"
)
def _can_inverse_transform(self):
return all(hasattr(t, "inverse_transform") for _, _, t in self._iter())
[docs] @available_if(_final_estimator_has("score"))
def score(self, X, y=None, sample_weight=None):
"""Transform the data, and apply `score` with the final estimator.
Call `transform` of each transformer in the pipeline. The transformed
data are finally passed to the final estimator that calls
`score` method. Only valid if the final estimator implements `score`.
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 : array-like, default=None
If not None, this argument is passed as ``sample_weight`` keyword
argument to the ``score`` method of the final estimator.
Returns
-------
score : float
Result of calling `score` on the final estimator.
"""
Xt = X
for _, name, transform in self._iter(with_final=False):
Xt = transform.transform(Xt)
score_params = {}
if sample_weight is not None:
score_params["sample_weight"] = sample_weight
return self.steps[-1][1].score(Xt, y, **score_params)
@property
def classes_(self):
"""The classes labels. Only exist if the last step is a classifier."""
return self.steps[-1][1].classes_
def _more_tags(self):
# check if first estimator expects pairwise input
return {"pairwise": _safe_tags(self.steps[0][1], "pairwise")}
[docs] def get_feature_names_out(self, input_features=None):
"""Get output feature names for transformation.
Transform input features using the pipeline.
Parameters
----------
input_features : array-like of str or None, default=None
Input features.
Returns
-------
feature_names_out : ndarray of str objects
Transformed feature names.
"""
feature_names_out = input_features
for _, name, transform in self._iter():
if not hasattr(transform, "get_feature_names_out"):
raise AttributeError(
"Estimator {} does not provide get_feature_names_out. "
"Did you mean to call pipeline[:-1].get_feature_names_out"
"()?".format(name)
)
feature_names_out = transform.get_feature_names_out(feature_names_out)
return feature_names_out
@property
def n_features_in_(self):
"""Number of features seen during first step `fit` method."""
# delegate to first step (which will call _check_is_fitted)
return self.steps[0][1].n_features_in_
@property
def feature_names_in_(self):
"""Names of features seen during first step `fit` method."""
# delegate to first step (which will call _check_is_fitted)
return self.steps[0][1].feature_names_in_
def __sklearn_is_fitted__(self):
"""Indicate whether pipeline has been fit."""
try:
# check if the last step of the pipeline is fitted
# we only check the last step since if the last step is fit, it
# means the previous steps should also be fit. This is faster than
# checking if every step of the pipeline is fit.
check_is_fitted(self.steps[-1][1])
return True
except NotFittedError:
return False
def _sk_visual_block_(self):
_, estimators = zip(*self.steps)
def _get_name(name, est):
if est is None or est == "passthrough":
return f"{name}: passthrough"
# Is an estimator
return f"{name}: {est.__class__.__name__}"
names = [_get_name(name, est) for name, est in self.steps]
name_details = [str(est) for est in estimators]
return _VisualBlock(
"serial",
estimators,
names=names,
name_details=name_details,
dash_wrapped=False,
)
def _name_estimators(estimators):
"""Generate names for estimators."""
names = [
estimator if isinstance(estimator, str) else type(estimator).__name__.lower()
for estimator in estimators
]
namecount = defaultdict(int)
for est, name in zip(estimators, names):
namecount[name] += 1
for k, v in list(namecount.items()):
if v == 1:
del namecount[k]
for i in reversed(range(len(estimators))):
name = names[i]
if name in namecount:
names[i] += "-%d" % namecount[name]
namecount[name] -= 1
return list(zip(names, estimators))
def make_pipeline(*steps, memory=None, verbose=False):
"""Construct a :class:`Pipeline` from the given estimators.
This is a shorthand for the :class:`Pipeline` constructor; it does not
require, and does not permit, naming the estimators. Instead, their names
will be set to the lowercase of their types automatically.
Parameters
----------
*steps : list of Estimator objects
List of the scikit-learn estimators that are chained together.
memory : str or object with the joblib.Memory interface, 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.
verbose : bool, default=False
If True, the time elapsed while fitting each step will be printed as it
is completed.
Returns
-------
p : Pipeline
Returns a scikit-learn :class:`Pipeline` object.
See Also
--------
Pipeline : Class for creating a pipeline of transforms with a final
estimator.
Examples
--------
>>> from sklearn.naive_bayes import GaussianNB
>>> from sklearn.preprocessing import StandardScaler
>>> from sklearn.pipeline import make_pipeline
>>> make_pipeline(StandardScaler(), GaussianNB(priors=None))
Pipeline(steps=[('standardscaler', StandardScaler()),
('gaussiannb', GaussianNB())])
"""
return Pipeline(_name_estimators(steps), memory=memory, verbose=verbose)
def _transform_one(transformer, X, y, weight, **fit_params):
res = transformer.transform(X)
# if we have a weight for this transformer, multiply output
if weight is None:
return res
return res * weight
def _fit_transform_one(
transformer, X, y, weight, message_clsname="", message=None, **fit_params
):
"""
Fits ``transformer`` to ``X`` and ``y``. The transformed result is returned
with the fitted transformer. If ``weight`` is not ``None``, the result will
be multiplied by ``weight``.
"""
with _print_elapsed_time(message_clsname, message):
if hasattr(transformer, "fit_transform"):
res = transformer.fit_transform(X, y, **fit_params)
else:
res = transformer.fit(X, y, **fit_params).transform(X)
if weight is None:
return res, transformer
return res * weight, transformer
def _fit_one(transformer, X, y, weight, message_clsname="", message=None, **fit_params):
"""
Fits ``transformer`` to ``X`` and ``y``.
"""
with _print_elapsed_time(message_clsname, message):
return transformer.fit(X, y, **fit_params)
class FeatureUnion(TransformerMixin, _BaseComposition):
"""Concatenates results of multiple transformer objects.
This estimator applies a list of transformer objects in parallel to the
input data, then concatenates the results. This is useful to combine
several feature extraction mechanisms into a single transformer.
Parameters of the transformers may be set using its name and the parameter
name separated by a '__'. A transformer may be replaced entirely by
setting the parameter with its name to another transformer, removed by
setting to 'drop' or disabled by setting to 'passthrough' (features are
passed without transformation).
Read more in the :ref:`User Guide <feature_union>`.
.. versionadded:: 0.13
Parameters
----------
transformer_list : list of (str, transformer) tuples
List of transformer objects to be applied to the data. The first
half of each tuple is the name of the transformer. The transformer can
be 'drop' for it to be ignored or can be 'passthrough' for features to
be passed unchanged.
.. versionadded:: 1.1
Added the option `"passthrough"`.
.. versionchanged:: 0.22
Deprecated `None` as a transformer in favor of 'drop'.
n_jobs : int, default=None
Number of jobs to run in parallel.
``None`` means 1 unless in a :obj:`joblib.parallel_backend` context.
``-1`` means using all processors. See :term:`Glossary <n_jobs>`
for more details.
.. versionchanged:: v0.20
`n_jobs` default changed from 1 to None
transformer_weights : dict, default=None
Multiplicative weights for features per transformer.
Keys are transformer names, values the weights.
Raises ValueError if key not present in ``transformer_list``.
verbose : bool, default=False
If True, the time elapsed while fitting each transformer will be
printed as it is completed.
Attributes
----------
n_features_in_ : int
Number of features seen during :term:`fit`. Only defined if the
underlying first transformer in `transformer_list` exposes such an
attribute when fit.
.. versionadded:: 0.24
See Also
--------
make_union : Convenience function for simplified feature union
construction.
Examples
--------
>>> from sklearn.pipeline import FeatureUnion
>>> from sklearn.decomposition import PCA, TruncatedSVD
>>> union = FeatureUnion([("pca", PCA(n_components=1)),
... ("svd", TruncatedSVD(n_components=2))])
>>> X = [[0., 1., 3], [2., 2., 5]]
>>> union.fit_transform(X)
array([[ 1.5 , 3.0..., 0.8...],
[-1.5 , 5.7..., -0.4...]])
"""
_required_parameters = ["transformer_list"]
def __init__(
self, transformer_list, *, n_jobs=None, transformer_weights=None, verbose=False
):
self.transformer_list = transformer_list
self.n_jobs = n_jobs
self.transformer_weights = transformer_weights
self.verbose = verbose
def get_params(self, deep=True):
"""Get parameters for this estimator.
Returns the parameters given in the constructor as well as the
estimators contained within the `transformer_list` of the
`FeatureUnion`.
Parameters
----------
deep : bool, default=True
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.
"""
return self._get_params("transformer_list", deep=deep)
def set_params(self, **kwargs):
"""Set the parameters of this estimator.
Valid parameter keys can be listed with ``get_params()``. Note that
you can directly set the parameters of the estimators contained in
`tranformer_list`.
Parameters
----------
**kwargs : dict
Parameters of this estimator or parameters of estimators contained
in `transform_list`. Parameters of the transformers may be set
using its name and the parameter name separated by a '__'.
Returns
-------
self : object
FeatureUnion class instance.
"""
self._set_params("transformer_list", **kwargs)
return self
def _validate_transformers(self):
names, transformers = zip(*self.transformer_list)
# validate names
self._validate_names(names)
# validate estimators
for t in transformers:
if t in ("drop", "passthrough"):
continue
if not (hasattr(t, "fit") or hasattr(t, "fit_transform")) or not hasattr(
t, "transform"
):
raise TypeError(
"All estimators should implement fit and "
"transform. '%s' (type %s) doesn't" % (t, type(t))
)
def _validate_transformer_weights(self):
if not self.transformer_weights:
return
transformer_names = set(name for name, _ in self.transformer_list)
for name in self.transformer_weights:
if name not in transformer_names:
raise ValueError(
f'Attempting to weight transformer "{name}", '
"but it is not present in transformer_list."
)
def _iter(self):
"""
Generate (name, trans, weight) tuples excluding None and
'drop' transformers.
"""
get_weight = (self.transformer_weights or {}).get
for name, trans in self.transformer_list:
if trans == "drop":
continue
if trans == "passthrough":
trans = FunctionTransformer()
yield (name, trans, get_weight(name))
@deprecated(
"get_feature_names is deprecated in 1.0 and will be removed "
"in 1.2. Please use get_feature_names_out instead."
)
def get_feature_names(self):
"""Get feature names from all transformers.
Returns
-------
feature_names : list of strings
Names of the features produced by transform.
"""
feature_names = []
for name, trans, weight in self._iter():
if not hasattr(trans, "get_feature_names"):
raise AttributeError(
"Transformer %s (type %s) does not provide get_feature_names."
% (str(name), type(trans).__name__)
)
feature_names.extend([name + "__" + f for f in trans.get_feature_names()])
return feature_names
def get_feature_names_out(self, input_features=None):
"""Get output feature names for transformation.
Parameters
----------
input_features : array-like of str or None, default=None
Input features.
Returns
-------
feature_names_out : ndarray of str objects
Transformed feature names.
"""
feature_names = []
for name, trans, _ in self._iter():
if not hasattr(trans, "get_feature_names_out"):
raise AttributeError(
"Transformer %s (type %s) does not provide get_feature_names_out."
% (str(name), type(trans).__name__)
)
feature_names.extend(
[f"{name}__{f}" for f in trans.get_feature_names_out(input_features)]
)
return np.asarray(feature_names, dtype=object)
def fit(self, X, y=None, **fit_params):
"""Fit all transformers using X.
Parameters
----------
X : iterable or array-like, depending on transformers
Input data, used to fit transformers.
y : array-like of shape (n_samples, n_outputs), default=None
Targets for supervised learning.
**fit_params : dict, default=None
Parameters to pass to the fit method of the estimator.
Returns
-------
self : object
FeatureUnion class instance.
"""
transformers = self._parallel_func(X, y, fit_params, _fit_one)
if not transformers:
# All transformers are None
return self
self._update_transformer_list(transformers)
return self
def fit_transform(self, X, y=None, **fit_params):
"""Fit all transformers, transform the data and concatenate results.
Parameters
----------
X : iterable or array-like, depending on transformers
Input data to be transformed.
y : array-like of shape (n_samples, n_outputs), default=None
Targets for supervised learning.
**fit_params : dict, default=None
Parameters to pass to the fit method of the estimator.
Returns
-------
X_t : array-like or sparse matrix of \
shape (n_samples, sum_n_components)
The `hstack` of results of transformers. `sum_n_components` is the
sum of `n_components` (output dimension) over transformers.
"""
results = self._parallel_func(X, y, fit_params, _fit_transform_one)
if not results:
# All transformers are None
return np.zeros((X.shape[0], 0))
Xs, transformers = zip(*results)
self._update_transformer_list(transformers)
return self._hstack(Xs)
def _log_message(self, name, idx, total):
if not self.verbose:
return None
return "(step %d of %d) Processing %s" % (idx, total, name)
def _parallel_func(self, X, y, fit_params, func):
"""Runs func in parallel on X and y"""
self.transformer_list = list(self.transformer_list)
self._validate_transformers()
self._validate_transformer_weights()
transformers = list(self._iter())
return Parallel(n_jobs=self.n_jobs)(
delayed(func)(
transformer,
X,
y,
weight,
message_clsname="FeatureUnion",
message=self._log_message(name, idx, len(transformers)),
**fit_params,
)
for idx, (name, transformer, weight) in enumerate(transformers, 1)
)
def transform(self, X):
"""Transform X separately by each transformer, concatenate results.
Parameters
----------
X : iterable or array-like, depending on transformers
Input data to be transformed.
Returns
-------
X_t : array-like or sparse matrix of \
shape (n_samples, sum_n_components)
The `hstack` of results of transformers. `sum_n_components` is the
sum of `n_components` (output dimension) over transformers.
"""
Xs = Parallel(n_jobs=self.n_jobs)(
delayed(_transform_one)(trans, X, None, weight)
for name, trans, weight in self._iter()
)
if not Xs:
# All transformers are None
return np.zeros((X.shape[0], 0))
return self._hstack(Xs)
def _hstack(self, Xs):
if any(sparse.issparse(f) for f in Xs):
Xs = sparse.hstack(Xs).tocsr()
else:
Xs = np.hstack(Xs)
return Xs
def _update_transformer_list(self, transformers):
transformers = iter(transformers)
self.transformer_list[:] = [
(name, old if old == "drop" else next(transformers))
for name, old in self.transformer_list
]
@property
def n_features_in_(self):
"""Number of features seen during :term:`fit`."""
# X is passed to all transformers so we just delegate to the first one
return self.transformer_list[0][1].n_features_in_
def __sklearn_is_fitted__(self):
# Delegate whether feature union was fitted
for _, transformer, _ in self._iter():
check_is_fitted(transformer)
return True
def _sk_visual_block_(self):
names, transformers = zip(*self.transformer_list)
return _VisualBlock("parallel", transformers, names=names)
def make_union(*transformers, n_jobs=None, verbose=False):
"""Construct a FeatureUnion from the given transformers.
This is a shorthand for the FeatureUnion constructor; it does not require,
and does not permit, naming the transformers. Instead, they will be given
names automatically based on their types. It also does not allow weighting.
Parameters
----------
*transformers : list of estimators
One or more estimators.
n_jobs : int, default=None
Number of jobs to run in parallel.
``None`` means 1 unless in a :obj:`joblib.parallel_backend` context.
``-1`` means using all processors. See :term:`Glossary <n_jobs>`
for more details.
.. versionchanged:: v0.20
`n_jobs` default changed from 1 to None.
verbose : bool, default=False
If True, the time elapsed while fitting each transformer will be
printed as it is completed.
Returns
-------
f : FeatureUnion
A :class:`FeatureUnion` object for concatenating the results of multiple
transformer objects.
See Also
--------
FeatureUnion : Class for concatenating the results of multiple transformer
objects.
Examples
--------
>>> from sklearn.decomposition import PCA, TruncatedSVD
>>> from sklearn.pipeline import make_union
>>> make_union(PCA(), TruncatedSVD())
FeatureUnion(transformer_list=[('pca', PCA()),
('truncatedsvd', TruncatedSVD())])
"""
return FeatureUnion(_name_estimators(transformers), n_jobs=n_jobs, verbose=verbose)