"""
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 warnings import warn
from abc import ABCMeta, abstractmethod
import numpy as np
from scipy import sparse
from .base import BaseEstimator, TransformerMixin
from .externals.joblib import Parallel, delayed
from .externals import six
from .utils import tosequence
from .utils.metaestimators import if_delegate_has_method
__all__ = ['Pipeline', 'FeatureUnion']
class _BasePipeline(six.with_metaclass(ABCMeta, BaseEstimator)):
"""Handles parameter management for classifiers composed of named steps.
"""
@abstractmethod
def __init__(self):
pass
def _replace_step(self, steps_attr, name, new_val):
# assumes `name` is a valid step name
new_steps = getattr(self, steps_attr)[:]
for i, (step_name, _) in enumerate(new_steps):
if step_name == name:
new_steps[i] = (name, new_val)
break
setattr(self, steps_attr, new_steps)
def _get_params(self, steps_attr, deep=True):
out = super(_BasePipeline, self).get_params(deep=False)
if not deep:
return out
steps = getattr(self, steps_attr)
out.update(steps)
for name, estimator in steps:
if estimator is None:
continue
for key, value in six.iteritems(estimator.get_params(deep=True)):
out['%s__%s' % (name, key)] = value
return out
def _set_params(self, steps_attr, **params):
# Ensure strict ordering of parameter setting:
# 1. All steps
if steps_attr in params:
setattr(self, steps_attr, params.pop(steps_attr))
# 2. Step replacement
step_names, _ = zip(*getattr(self, steps_attr))
for name in list(six.iterkeys(params)):
if '__' not in name and name in step_names:
self._replace_step(steps_attr, name, params.pop(name))
# 3. Step parameters and other initilisation arguments
super(_BasePipeline, self).set_params(**params)
return self
def _validate_names(self, names):
if len(set(names)) != len(names):
raise ValueError('Names provided are not unique: '
'{0!r}'.format(list(names)))
invalid_names = set(names).intersection(self.get_params(deep=False))
if invalid_names:
raise ValueError('Step names conflict with constructor arguments: '
'{0!r}'.format(sorted(invalid_names)))
invalid_names = [name for name in names if '__' in name]
if invalid_names:
raise ValueError('Step names must not contain __: got '
'{0!r}'.format(invalid_names))
class Pipeline(_BasePipeline):
"""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 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
to None.
Read more in the :ref:`User Guide <pipeline>`.
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.
Attributes
----------
named_steps : dict
Read-only attribute to access any step parameter by user given name.
Keys are step names and values are steps parameters.
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 SVM-C
>>> 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)
... # doctest: +ELLIPSIS
Pipeline(steps=[...])
>>> prediction = anova_svm.predict(X)
>>> anova_svm.score(X, y) # doctest: +ELLIPSIS
0.829...
>>> # getting the selected features chosen by anova_filter
>>> anova_svm.named_steps['anova'].get_support()
... # doctest: +NORMALIZE_WHITESPACE
array([False, False, True, True, False, False, True, True, False,
True, False, True, True, False, True, False, True, True,
False, False], dtype=bool)
"""
# BaseEstimator interface
def __init__(self, steps):
# shallow copy of steps
self.steps = tosequence(steps)
self._validate_steps()
[docs] def get_params(self, deep=True):
"""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.
"""
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()``.
Returns
-------
self
"""
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:
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."
" '%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 not hasattr(estimator, "fit"):
raise TypeError("Last step of Pipeline should implement fit. "
"'%s' (type %s) doesn't"
% (estimator, type(estimator)))
@property
def _estimator_type(self):
return self.steps[-1][1]._estimator_type
@property
def named_steps(self):
return dict(self.steps)
@property
def _final_estimator(self):
return self.steps[-1][1]
# Estimator interface
def _fit(self, X, y=None, **fit_params):
self._validate_steps()
fit_params_steps = dict((name, {}) for name, step in self.steps
if step is not None)
for pname, pval in six.iteritems(fit_params):
step, param = pname.split('__', 1)
fit_params_steps[step][param] = pval
Xt = X
for name, transform in self.steps[:-1]:
if transform is None:
pass
elif hasattr(transform, "fit_transform"):
Xt = transform.fit_transform(Xt, y, **fit_params_steps[name])
else:
Xt = transform.fit(Xt, y, **fit_params_steps[name]) \
.transform(Xt)
if self._final_estimator is None:
return Xt, {}
return Xt, fit_params_steps[self.steps[-1][0]]
def fit(self, X, y=None, **fit_params):
"""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 parameter ``p`` for step
``s`` has key ``s__p``.
Returns
-------
self : Pipeline
This estimator
"""
Xt, fit_params = self._fit(X, y, **fit_params)
if self._final_estimator is not None:
self._final_estimator.fit(Xt, y, **fit_params)
return self
def fit_transform(self, X, y=None, **fit_params):
"""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 parameter ``p`` for step
``s`` has key ``s__p``.
Returns
-------
Xt : array-like, shape = [n_samples, n_transformed_features]
Transformed samples
"""
last_step = self._final_estimator
Xt, fit_params = self._fit(X, y, **fit_params)
if hasattr(last_step, 'fit_transform'):
return last_step.fit_transform(Xt, y, **fit_params)
elif last_step is None:
return Xt
else:
return last_step.fit(Xt, y, **fit_params).transform(Xt)
@if_delegate_has_method(delegate='_final_estimator')
def predict(self, X):
"""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.
Returns
-------
y_pred : array-like
"""
Xt = X
for name, transform in self.steps[:-1]:
if transform is not None:
Xt = transform.transform(Xt)
return self.steps[-1][-1].predict(Xt)
@if_delegate_has_method(delegate='_final_estimator')
def fit_predict(self, X, y=None, **fit_params):
"""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 parameter ``p`` for step
``s`` has key ``s__p``.
Returns
-------
y_pred : array-like
"""
Xt, fit_params = self._fit(X, y, **fit_params)
return self.steps[-1][-1].fit_predict(Xt, y, **fit_params)
@if_delegate_has_method(delegate='_final_estimator')
def predict_proba(self, X):
"""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 : array-like, shape = [n_samples, n_classes]
"""
Xt = X
for name, transform in self.steps[:-1]:
if transform is not None:
Xt = transform.transform(Xt)
return self.steps[-1][-1].predict_proba(Xt)
@if_delegate_has_method(delegate='_final_estimator')
def decision_function(self, X):
"""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 : array-like, shape = [n_samples, n_classes]
"""
Xt = X
for name, transform in self.steps[:-1]:
if transform is not None:
Xt = transform.transform(Xt)
return self.steps[-1][-1].decision_function(Xt)
@if_delegate_has_method(delegate='_final_estimator')
def predict_log_proba(self, X):
"""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 : array-like, shape = [n_samples, n_classes]
"""
Xt = X
for name, transform in self.steps[:-1]:
if transform is not None:
Xt = transform.transform(Xt)
return self.steps[-1][-1].predict_log_proba(Xt)
@property
def transform(self):
"""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 : array-like, shape = [n_samples, n_transformed_features]
"""
# _final_estimator is None or has transform, otherwise attribute error
if self._final_estimator is not None:
self._final_estimator.transform
return self._transform
def _transform(self, X):
Xt = X
for name, transform in self.steps:
if transform is not None:
Xt = transform.transform(Xt)
return Xt
@property
def inverse_transform(self):
"""Apply inverse transformations in reverse order
All estimators in the pipeline must support ``inverse_transform``.
Parameters
----------
Xt : array-like, shape = [n_samples, n_transformed_features]
Data samples, where ``n_samples`` is the number of samples and
``n_features`` is the number of features. Must fulfill
input requirements of last step of pipeline's
``inverse_transform`` method.
Returns
-------
Xt : array-like, shape = [n_samples, n_features]
"""
# raise AttributeError if necessary for hasattr behaviour
for name, transform in self.steps:
if transform is not None:
transform.inverse_transform
return self._inverse_transform
def _inverse_transform(self, X):
if hasattr(X, 'ndim') and X.ndim == 1:
warn("From version 0.19, a 1d X will not be reshaped in"
" pipeline.inverse_transform any more.", FutureWarning)
X = X[None, :]
Xt = X
for name, transform in self.steps[::-1]:
if transform is not None:
Xt = transform.inverse_transform(Xt)
return Xt
@if_delegate_has_method(delegate='_final_estimator')
def score(self, X, y=None):
"""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.
Returns
-------
score : float
"""
Xt = X
for name, transform in self.steps[:-1]:
if transform is not None:
Xt = transform.transform(Xt)
return self.steps[-1][-1].score(Xt, y)
@property
def classes_(self):
return self.steps[-1][-1].classes_
@property
def _pairwise(self):
# check if first estimator expects pairwise input
return getattr(self.steps[0][1], '_pairwise', False)
def _name_estimators(estimators):
"""Generate names for estimators."""
names = [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(six.iteritems(namecount)):
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):
"""Construct a Pipeline from the given estimators.
This is a shorthand for the 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.
Examples
--------
>>> from sklearn.naive_bayes import GaussianNB
>>> from sklearn.preprocessing import StandardScaler
>>> make_pipeline(StandardScaler(), GaussianNB(priors=None))
... # doctest: +NORMALIZE_WHITESPACE
Pipeline(steps=[('standardscaler',
StandardScaler(copy=True, with_mean=True, with_std=True)),
('gaussiannb', GaussianNB(priors=None))])
Returns
-------
p : Pipeline
"""
return Pipeline(_name_estimators(steps))
def _fit_one_transformer(transformer, X, y):
return transformer.fit(X, y)
def _transform_one(transformer, name, weight, X):
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, name, weight, X, y,
**fit_params):
if hasattr(transformer, 'fit_transform'):
res = transformer.fit_transform(X, y, **fit_params)
else:
res = transformer.fit(X, y, **fit_params).transform(X)
# if we have a weight for this transformer, multiply output
if weight is None:
return res, transformer
return res * weight, transformer
class FeatureUnion(_BasePipeline, TransformerMixin):
"""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,
or removed by setting to ``None``.
Read more in the :ref:`User Guide <feature_union>`.
Parameters
----------
transformer_list: list of (string, transformer) tuples
List of transformer objects to be applied to the data. The first
half of each tuple is the name of the transformer.
n_jobs: int, optional
Number of jobs to run in parallel (default 1).
transformer_weights: dict, optional
Multiplicative weights for features per transformer.
Keys are transformer names, values the weights.
"""
def __init__(self, transformer_list, n_jobs=1, transformer_weights=None):
self.transformer_list = tosequence(transformer_list)
self.n_jobs = n_jobs
self.transformer_weights = transformer_weights
self._validate_transformers()
def get_params(self, deep=True):
"""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.
"""
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()``.
Returns
-------
self
"""
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 is None:
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 _iter(self):
"""Generate (name, est, weight) tuples excluding None transformers
"""
get_weight = (self.transformer_weights or {}).get
return ((name, trans, get_weight(name))
for name, trans in self.transformer_list
if trans is not None)
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 fit(self, X, y=None):
"""Fit all transformers using X.
Parameters
----------
X : iterable or array-like, depending on transformers
Input data, used to fit transformers.
y : array-like, shape (n_samples, ...), optional
Targets for supervised learning.
Returns
-------
self : FeatureUnion
This estimator
"""
self._validate_transformers()
transformers = Parallel(n_jobs=self.n_jobs)(
delayed(_fit_one_transformer)(trans, X, y)
for _, trans, _ in self._iter())
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, shape (n_samples, ...), optional
Targets for supervised learning.
Returns
-------
X_t : array-like or sparse matrix, shape (n_samples, sum_n_components)
hstack of results of transformers. sum_n_components is the
sum of n_components (output dimension) over transformers.
"""
self._validate_transformers()
result = Parallel(n_jobs=self.n_jobs)(
delayed(_fit_transform_one)(trans, name, weight, X, y,
**fit_params)
for name, trans, weight in self._iter())
if not result:
# All transformers are None
return np.zeros((X.shape[0], 0))
Xs, transformers = zip(*result)
self._update_transformer_list(transformers)
if any(sparse.issparse(f) for f in Xs):
Xs = sparse.hstack(Xs).tocsr()
else:
Xs = np.hstack(Xs)
return Xs
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, shape (n_samples, sum_n_components)
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, name, weight, X)
for name, trans, weight in self._iter())
if not Xs:
# All transformers are None
return np.zeros((X.shape[0], 0))
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, None if old is None else next(transformers))
for name, old in self.transformer_list
]
# XXX it would be nice to have a keyword-only n_jobs argument to this function,
# but that's not allowed in Python 2.x.
def make_union(*transformers):
"""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.
Examples
--------
>>> from sklearn.decomposition import PCA, TruncatedSVD
>>> make_union(PCA(), TruncatedSVD()) # doctest: +NORMALIZE_WHITESPACE
FeatureUnion(n_jobs=1,
transformer_list=[('pca',
PCA(copy=True, iterated_power='auto',
n_components=None, random_state=None,
svd_solver='auto', tol=0.0, whiten=False)),
('truncatedsvd',
TruncatedSVD(algorithm='randomized',
n_components=2, n_iter=5,
random_state=None, tol=0.0))],
transformer_weights=None)
Returns
-------
f : FeatureUnion
"""
return FeatureUnion(_name_estimators(transformers))