""" The :mod:`sklearn.compose._column_transformer` module implements utilities to work with heterogeneous data and to apply different transformers to different columns. """ # Author: Andreas Mueller # Joris Van den Bossche # License: BSD from itertools import chain import numpy as np from scipy import sparse from joblib import Parallel from ..base import clone, TransformerMixin from ..utils._estimator_html_repr import _VisualBlock from ..pipeline import _fit_transform_one, _transform_one, _name_estimators from ..preprocessing import FunctionTransformer from ..utils import Bunch from ..utils import _safe_indexing from ..utils import _get_column_indices from ..utils import _determine_key_type from ..utils.metaestimators import _BaseComposition from ..utils.validation import check_array, check_is_fitted from ..utils.validation import _deprecate_positional_args from ..utils.fixes import delayed __all__ = [ 'ColumnTransformer', 'make_column_transformer', 'make_column_selector' ] _ERR_MSG_1DCOLUMN = ("1D data passed to a transformer that expects 2D data. " "Try to specify the column selection as a list of one " "item instead of a scalar.") class ColumnTransformer(TransformerMixin, _BaseComposition): """Applies transformers to columns of an array or pandas DataFrame. This estimator allows different columns or column subsets of the input to be transformed separately and the features generated by each transformer will be concatenated to form a single feature space. This is useful for heterogeneous or columnar data, to combine several feature extraction mechanisms or transformations into a single transformer. Read more in the :ref:`User Guide `. .. versionadded:: 0.20 Parameters ---------- transformers : list of tuples List of (name, transformer, columns) tuples specifying the transformer objects to be applied to subsets of the data. name : str Like in Pipeline and FeatureUnion, this allows the transformer and its parameters to be set using ``set_params`` and searched in grid search. transformer : {'drop', 'passthrough'} or estimator Estimator must support :term:`fit` and :term:`transform`. Special-cased strings 'drop' and 'passthrough' are accepted as well, to indicate to drop the columns or to pass them through untransformed, respectively. columns : str, array-like of str, int, array-like of int, \ array-like of bool, slice or callable Indexes the data on its second axis. Integers are interpreted as positional columns, while strings can reference DataFrame columns by name. A scalar string or int should be used where ``transformer`` expects X to be a 1d array-like (vector), otherwise a 2d array will be passed to the transformer. A callable is passed the input data `X` and can return any of the above. To select multiple columns by name or dtype, you can use :obj:`make_column_selector`. remainder : {'drop', 'passthrough'} or estimator, default='drop' By default, only the specified columns in `transformers` are transformed and combined in the output, and the non-specified columns are dropped. (default of ``'drop'``). By specifying ``remainder='passthrough'``, all remaining columns that were not specified in `transformers` will be automatically passed through. This subset of columns is concatenated with the output of the transformers. By setting ``remainder`` to be an estimator, the remaining non-specified columns will use the ``remainder`` estimator. The estimator must support :term:`fit` and :term:`transform`. Note that using this feature requires that the DataFrame columns input at :term:`fit` and :term:`transform` have identical order. sparse_threshold : float, default=0.3 If the output of the different transformers contains sparse matrices, these will be stacked as a sparse matrix if the overall density is lower than this value. Use ``sparse_threshold=0`` to always return dense. When the transformed output consists of all dense data, the stacked result will be dense, and this keyword will be ignored. 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 ` for more details. transformer_weights : dict, default=None Multiplicative weights for features per transformer. The output of the transformer is multiplied by these weights. Keys are transformer names, values the weights. verbose : bool, default=False If True, the time elapsed while fitting each transformer will be printed as it is completed. Attributes ---------- transformers_ : list The collection of fitted transformers as tuples of (name, fitted_transformer, column). `fitted_transformer` can be an estimator, 'drop', or 'passthrough'. In case there were no columns selected, this will be the unfitted transformer. If there are remaining columns, the final element is a tuple of the form: ('remainder', transformer, remaining_columns) corresponding to the ``remainder`` parameter. If there are remaining columns, then ``len(transformers_)==len(transformers)+1``, otherwise ``len(transformers_)==len(transformers)``. named_transformers_ : :class:`~sklearn.utils.Bunch` Read-only attribute to access any transformer by given name. Keys are transformer names and values are the fitted transformer objects. sparse_output_ : bool Boolean flag indicating whether the output of ``transform`` is a sparse matrix or a dense numpy array, which depends on the output of the individual transformers and the `sparse_threshold` keyword. Notes ----- The order of the columns in the transformed feature matrix follows the order of how the columns are specified in the `transformers` list. Columns of the original feature matrix that are not specified are dropped from the resulting transformed feature matrix, unless specified in the `passthrough` keyword. Those columns specified with `passthrough` are added at the right to the output of the transformers. See Also -------- make_column_transformer : Convenience function for combining the outputs of multiple transformer objects applied to column subsets of the original feature space. make_column_selector : Convenience function for selecting columns based on datatype or the columns name with a regex pattern. Examples -------- >>> import numpy as np >>> from sklearn.compose import ColumnTransformer >>> from sklearn.preprocessing import Normalizer >>> ct = ColumnTransformer( ... [("norm1", Normalizer(norm='l1'), [0, 1]), ... ("norm2", Normalizer(norm='l1'), slice(2, 4))]) >>> X = np.array([[0., 1., 2., 2.], ... [1., 1., 0., 1.]]) >>> # Normalizer scales each row of X to unit norm. A separate scaling >>> # is applied for the two first and two last elements of each >>> # row independently. >>> ct.fit_transform(X) array([[0. , 1. , 0.5, 0.5], [0.5, 0.5, 0. , 1. ]]) """ _required_parameters = ['transformers'] @_deprecate_positional_args def __init__(self, transformers, *, remainder='drop', sparse_threshold=0.3, n_jobs=None, transformer_weights=None, verbose=False): self.transformers = transformers self.remainder = remainder self.sparse_threshold = sparse_threshold self.n_jobs = n_jobs self.transformer_weights = transformer_weights self.verbose = verbose @property def _transformers(self): """ Internal list of transformer only containing the name and transformers, dropping the columns. This is for the implementation of get_params via BaseComposition._get_params which expects lists of tuples of len 2. """ return [(name, trans) for name, trans, _ in self.transformers] @_transformers.setter def _transformers(self, value): self.transformers = [ (name, trans, col) for ((name, trans), (_, _, col)) in zip(value, self.transformers)] 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 `transformers` of the `ColumnTransformer`. Parameters ---------- deep : bool, default=True If True, will return the parameters for this estimator and contained subobjects that are estimators. Returns ------- params : dict Parameter names mapped to their values. """ return self._get_params('_transformers', 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 `transformers` of `ColumnTransformer`. Returns ------- self """ self._set_params('_transformers', **kwargs) return self def _iter(self, fitted=False, replace_strings=False): """ Generate (name, trans, column, weight) tuples. If fitted=True, use the fitted transformers, else use the user specified transformers updated with converted column names and potentially appended with transformer for remainder. """ if fitted: transformers = self.transformers_ else: # interleave the validated column specifiers transformers = [ (name, trans, column) for (name, trans, _), column in zip(self.transformers, self._columns) ] # add transformer tuple for remainder if self._remainder[2] is not None: transformers = chain(transformers, [self._remainder]) get_weight = (self.transformer_weights or {}).get for name, trans, column in transformers: if replace_strings: # replace 'passthrough' with identity transformer and # skip in case of 'drop' if trans == 'passthrough': trans = FunctionTransformer( accept_sparse=True, check_inverse=False ) elif trans == 'drop': continue elif _is_empty_column_selection(column): continue yield (name, trans, column, get_weight(name)) def _validate_transformers(self): if not self.transformers: return names, transformers, _ = zip(*self.transformers) # 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, or can be 'drop' or 'passthrough' " "specifiers. '%s' (type %s) doesn't." % (t, type(t))) def _validate_column_callables(self, X): """ Converts callable column specifications. """ columns = [] for _, _, column in self.transformers: if callable(column): column = column(X) columns.append(column) self._columns = columns def _validate_remainder(self, X): """ Validates ``remainder`` and defines ``_remainder`` targeting the remaining columns. """ is_transformer = ((hasattr(self.remainder, "fit") or hasattr(self.remainder, "fit_transform")) and hasattr(self.remainder, "transform")) if (self.remainder not in ('drop', 'passthrough') and not is_transformer): raise ValueError( "The remainder keyword needs to be one of 'drop', " "'passthrough', or estimator. '%s' was passed instead" % self.remainder) # Make it possible to check for reordered named columns on transform self._has_str_cols = any(_determine_key_type(cols) == 'str' for cols in self._columns) if hasattr(X, 'columns'): self._df_columns = X.columns self._n_features = X.shape[1] cols = [] for columns in self._columns: cols.extend(_get_column_indices(X, columns)) remaining_idx = sorted(set(range(self._n_features)) - set(cols)) self._remainder = ('remainder', self.remainder, remaining_idx or None) @property def named_transformers_(self): """Access the fitted transformer by name. Read-only attribute to access any transformer by given name. Keys are transformer names and values are the fitted transformer objects. """ # Use Bunch object to improve autocomplete return Bunch(**{name: trans for name, trans, _ in self.transformers_}) def get_feature_names(self): """Get feature names from all transformers. Returns ------- feature_names : list of strings Names of the features produced by transform. """ check_is_fitted(self) feature_names = [] for name, trans, column, _ in self._iter(fitted=True): if trans == 'drop' or _is_empty_column_selection(column): continue if trans == 'passthrough': if hasattr(self, '_df_columns'): if ((not isinstance(column, slice)) and all(isinstance(col, str) for col in column)): feature_names.extend(column) else: feature_names.extend(self._df_columns[column]) else: indices = np.arange(self._n_features) feature_names.extend(['x%d' % i for i in indices[column]]) continue 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 _update_fitted_transformers(self, transformers): # transformers are fitted; excludes 'drop' cases fitted_transformers = iter(transformers) transformers_ = [] for name, old, column, _ in self._iter(): if old == 'drop': trans = 'drop' elif old == 'passthrough': # FunctionTransformer is present in list of transformers, # so get next transformer, but save original string next(fitted_transformers) trans = 'passthrough' elif _is_empty_column_selection(column): trans = old else: trans = next(fitted_transformers) transformers_.append((name, trans, column)) # sanity check that transformers is exhausted assert not list(fitted_transformers) self.transformers_ = transformers_ def _validate_output(self, result): """ Ensure that the output of each transformer is 2D. Otherwise hstack can raise an error or produce incorrect results. """ names = [name for name, _, _, _ in self._iter(fitted=True, replace_strings=True)] for Xs, name in zip(result, names): if not getattr(Xs, 'ndim', 0) == 2: raise ValueError( "The output of the '{0}' transformer should be 2D (scipy " "matrix, array, or pandas DataFrame).".format(name)) def _log_message(self, name, idx, total): if not self.verbose: return None return '(%d of %d) Processing %s' % (idx, total, name) def _fit_transform(self, X, y, func, fitted=False): """ Private function to fit and/or transform on demand. Return value (transformers and/or transformed X data) depends on the passed function. ``fitted=True`` ensures the fitted transformers are used. """ transformers = list( self._iter(fitted=fitted, replace_strings=True)) try: return Parallel(n_jobs=self.n_jobs)( delayed(func)( transformer=clone(trans) if not fitted else trans, X=_safe_indexing(X, column, axis=1), y=y, weight=weight, message_clsname='ColumnTransformer', message=self._log_message(name, idx, len(transformers))) for idx, (name, trans, column, weight) in enumerate( self._iter(fitted=fitted, replace_strings=True), 1)) except ValueError as e: if "Expected 2D array, got 1D array instead" in str(e): raise ValueError(_ERR_MSG_1DCOLUMN) from e else: raise def fit(self, X, y=None): """Fit all transformers using X. Parameters ---------- X : {array-like, dataframe} of shape (n_samples, n_features) Input data, of which specified subsets are used to fit the transformers. y : array-like of shape (n_samples,...), default=None Targets for supervised learning. Returns ------- self : ColumnTransformer This estimator """ # we use fit_transform to make sure to set sparse_output_ (for which we # need the transformed data) to have consistent output type in predict self.fit_transform(X, y=y) return self def fit_transform(self, X, y=None): """Fit all transformers, transform the data and concatenate results. Parameters ---------- X : {array-like, dataframe} of shape (n_samples, n_features) Input data, of which specified subsets are used to fit the transformers. y : array-like of shape (n_samples,), default=None Targets for supervised learning. Returns ------- X_t : {array-like, sparse matrix} of \ shape (n_samples, sum_n_components) hstack of results of transformers. sum_n_components is the sum of n_components (output dimension) over transformers. If any result is a sparse matrix, everything will be converted to sparse matrices. """ # TODO: this should be `feature_names_in_` when we start having it if hasattr(X, "columns"): self._feature_names_in = np.asarray(X.columns) else: self._feature_names_in = None X = _check_X(X) # set n_features_in_ attribute self._check_n_features(X, reset=True) self._validate_transformers() self._validate_column_callables(X) self._validate_remainder(X) result = self._fit_transform(X, y, _fit_transform_one) if not result: self._update_fitted_transformers([]) # All transformers are None return np.zeros((X.shape[0], 0)) Xs, transformers = zip(*result) # determine if concatenated output will be sparse or not if any(sparse.issparse(X) for X in Xs): nnz = sum(X.nnz if sparse.issparse(X) else X.size for X in Xs) total = sum(X.shape[0] * X.shape[1] if sparse.issparse(X) else X.size for X in Xs) density = nnz / total self.sparse_output_ = density < self.sparse_threshold else: self.sparse_output_ = False self._update_fitted_transformers(transformers) self._validate_output(Xs) return self._hstack(list(Xs)) def transform(self, X): """Transform X separately by each transformer, concatenate results. Parameters ---------- X : {array-like, dataframe} of shape (n_samples, n_features) The data to be transformed by subset. Returns ------- X_t : {array-like, sparse matrix} of \ shape (n_samples, sum_n_components) hstack of results of transformers. sum_n_components is the sum of n_components (output dimension) over transformers. If any result is a sparse matrix, everything will be converted to sparse matrices. """ check_is_fitted(self) X = _check_X(X) if hasattr(X, "columns"): X_feature_names = np.asarray(X.columns) else: X_feature_names = None self._check_n_features(X, reset=False) if (self._feature_names_in is not None and X_feature_names is not None and np.any(self._feature_names_in != X_feature_names)): raise RuntimeError( "Given feature/column names do not match the ones for the " "data given during fit." ) Xs = self._fit_transform(X, None, _transform_one, fitted=True) self._validate_output(Xs) if not Xs: # All transformers are None return np.zeros((X.shape[0], 0)) return self._hstack(list(Xs)) def _hstack(self, Xs): """Stacks Xs horizontally. This allows subclasses to control the stacking behavior, while reusing everything else from ColumnTransformer. Parameters ---------- Xs : list of {array-like, sparse matrix, dataframe} """ if self.sparse_output_: try: # since all columns should be numeric before stacking them # in a sparse matrix, `check_array` is used for the # dtype conversion if necessary. converted_Xs = [check_array(X, accept_sparse=True, force_all_finite=False) for X in Xs] except ValueError as e: raise ValueError( "For a sparse output, all columns should " "be a numeric or convertible to a numeric." ) from e return sparse.hstack(converted_Xs).tocsr() else: Xs = [f.toarray() if sparse.issparse(f) else f for f in Xs] return np.hstack(Xs) def _sk_visual_block_(self): if isinstance(self.remainder, str) and self.remainder == 'drop': transformers = self.transformers elif hasattr(self, "_remainder"): remainder_columns = self._remainder[2] if hasattr(self, '_df_columns'): remainder_columns = ( self._df_columns[remainder_columns].tolist() ) transformers = chain(self.transformers, [('remainder', self.remainder, remainder_columns)]) else: transformers = chain(self.transformers, [('remainder', self.remainder, '')]) names, transformers, name_details = zip(*transformers) return _VisualBlock('parallel', transformers, names=names, name_details=name_details) def _check_X(X): """Use check_array only on lists and other non-array-likes / sparse""" if hasattr(X, '__array__') or sparse.issparse(X): return X return check_array(X, force_all_finite='allow-nan', dtype=object) def _is_empty_column_selection(column): """ Return True if the column selection is empty (empty list or all-False boolean array). """ if hasattr(column, 'dtype') and np.issubdtype(column.dtype, np.bool_): return not column.any() elif hasattr(column, '__len__'): return (len(column) == 0 or all(isinstance(col, bool) for col in column) and not any(column)) else: return False def _get_transformer_list(estimators): """ Construct (name, trans, column) tuples from list """ transformers, columns = zip(*estimators) names, _ = zip(*_name_estimators(transformers)) transformer_list = list(zip(names, transformers, columns)) return transformer_list def make_column_transformer(*transformers, remainder='drop', sparse_threshold=0.3, n_jobs=None, verbose=False): """Construct a ColumnTransformer from the given transformers. This is a shorthand for the ColumnTransformer 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 with ``transformer_weights``. Read more in the :ref:`User Guide `. Parameters ---------- *transformers : tuples Tuples of the form (transformer, columns) specifying the transformer objects to be applied to subsets of the data. transformer : {'drop', 'passthrough'} or estimator Estimator must support :term:`fit` and :term:`transform`. Special-cased strings 'drop' and 'passthrough' are accepted as well, to indicate to drop the columns or to pass them through untransformed, respectively. columns : str, array-like of str, int, array-like of int, slice, \ array-like of bool or callable Indexes the data on its second axis. Integers are interpreted as positional columns, while strings can reference DataFrame columns by name. A scalar string or int should be used where ``transformer`` expects X to be a 1d array-like (vector), otherwise a 2d array will be passed to the transformer. A callable is passed the input data `X` and can return any of the above. To select multiple columns by name or dtype, you can use :obj:`make_column_selector`. remainder : {'drop', 'passthrough'} or estimator, default='drop' By default, only the specified columns in `transformers` are transformed and combined in the output, and the non-specified columns are dropped. (default of ``'drop'``). By specifying ``remainder='passthrough'``, all remaining columns that were not specified in `transformers` will be automatically passed through. This subset of columns is concatenated with the output of the transformers. By setting ``remainder`` to be an estimator, the remaining non-specified columns will use the ``remainder`` estimator. The estimator must support :term:`fit` and :term:`transform`. sparse_threshold : float, default=0.3 If the transformed output consists of a mix of sparse and dense data, it will be stacked as a sparse matrix if the density is lower than this value. Use ``sparse_threshold=0`` to always return dense. When the transformed output consists of all sparse or all dense data, the stacked result will be sparse or dense, respectively, and this keyword will be ignored. 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 ` for more details. verbose : bool, default=False If True, the time elapsed while fitting each transformer will be printed as it is completed. Returns ------- ct : ColumnTransformer See Also -------- ColumnTransformer : Class that allows combining the outputs of multiple transformer objects used on column subsets of the data into a single feature space. Examples -------- >>> from sklearn.preprocessing import StandardScaler, OneHotEncoder >>> from sklearn.compose import make_column_transformer >>> make_column_transformer( ... (StandardScaler(), ['numerical_column']), ... (OneHotEncoder(), ['categorical_column'])) ColumnTransformer(transformers=[('standardscaler', StandardScaler(...), ['numerical_column']), ('onehotencoder', OneHotEncoder(...), ['categorical_column'])]) """ # transformer_weights keyword is not passed through because the user # would need to know the automatically generated names of the transformers transformer_list = _get_transformer_list(transformers) return ColumnTransformer(transformer_list, n_jobs=n_jobs, remainder=remainder, sparse_threshold=sparse_threshold, verbose=verbose) class make_column_selector: """Create a callable to select columns to be used with :class:`ColumnTransformer`. :func:`make_column_selector` can select columns based on datatype or the columns name with a regex. When using multiple selection criteria, **all** criteria must match for a column to be selected. Parameters ---------- pattern : str, default=None Name of columns containing this regex pattern will be included. If None, column selection will not be selected based on pattern. dtype_include : column dtype or list of column dtypes, default=None A selection of dtypes to include. For more details, see :meth:`pandas.DataFrame.select_dtypes`. dtype_exclude : column dtype or list of column dtypes, default=None A selection of dtypes to exclude. For more details, see :meth:`pandas.DataFrame.select_dtypes`. Returns ------- selector : callable Callable for column selection to be used by a :class:`ColumnTransformer`. See Also -------- ColumnTransformer : Class that allows combining the outputs of multiple transformer objects used on column subsets of the data into a single feature space. Examples -------- >>> from sklearn.preprocessing import StandardScaler, OneHotEncoder >>> from sklearn.compose import make_column_transformer >>> from sklearn.compose import make_column_selector >>> import pandas as pd # doctest: +SKIP >>> X = pd.DataFrame({'city': ['London', 'London', 'Paris', 'Sallisaw'], ... 'rating': [5, 3, 4, 5]}) # doctest: +SKIP >>> ct = make_column_transformer( ... (StandardScaler(), ... make_column_selector(dtype_include=np.number)), # rating ... (OneHotEncoder(), ... make_column_selector(dtype_include=object))) # city >>> ct.fit_transform(X) # doctest: +SKIP array([[ 0.90453403, 1. , 0. , 0. ], [-1.50755672, 1. , 0. , 0. ], [-0.30151134, 0. , 1. , 0. ], [ 0.90453403, 0. , 0. , 1. ]]) """ @_deprecate_positional_args def __init__(self, pattern=None, *, dtype_include=None, dtype_exclude=None): self.pattern = pattern self.dtype_include = dtype_include self.dtype_exclude = dtype_exclude def __call__(self, df): """Callable for column selection to be used by a :class:`ColumnTransformer`. Parameters ---------- df : dataframe of shape (n_features, n_samples) DataFrame to select columns from. """ if not hasattr(df, 'iloc'): raise ValueError("make_column_selector can only be applied to " "pandas dataframes") df_row = df.iloc[:1] if self.dtype_include is not None or self.dtype_exclude is not None: df_row = df_row.select_dtypes(include=self.dtype_include, exclude=self.dtype_exclude) cols = df_row.columns if self.pattern is not None: cols = cols[cols.str.contains(self.pattern, regex=True)] return cols.tolist()