scikit-learn · jnothman · Apr 29, 2020 · Jun 25, 2019 · Jun 25, 2019 · Jun 28, 2019
diff --git a/doc/modules/classes.rst b/doc/modules/classes.rst
@@ -1569,6 +1569,7 @@ Plotting
    utils.deprecated
    utils.estimator_checks.check_estimator
    utils.estimator_checks.parametrize_with_checks
+   utils.estimator_html_repr
    utils.extmath.safe_sparse_dot
    utils.extmath.randomized_range_finder
    utils.extmath.randomized_svd

diff --git a/doc/modules/compose.rst b/doc/modules/compose.rst
@@ -528,6 +528,31 @@ above example would be::
                                   ('countvectorizer', CountVectorizer(),
                                    'title')])
 
+.. _visualizing_composite_estimators:
+
+Visualizing Composite Estimators
+================================
+
+Estimators can be displayed with a HTML representation when shown in a
+jupyter notebook. This can be useful to diagnose or visualize a Pipeline with
+many estimators. This visualization is activated by setting the
+`display` option in :func:`sklearn.set_config`::
+
+  >>> from sklearn import set_config
+  >>> set_config(display='diagram')   # doctest: +SKIP
+  >>> # diplays HTML representation in a jupyter context
+  >>> column_trans  # doctest: +SKIP
+
+An example of the HTML output can be seen in the 
+**HTML representation of Pipeline** section of 
+:ref:`sphx_glr_auto_examples_compose_plot_column_transformer_mixed_types.py`.
+As an alternative, the HTML can be written to a file using
+:func:`~sklearn.utils.estimator_html_repr`::
+
+   >>> from sklearn.utils import estimator_html_repr
+   >>> with open('my_estimator.html', 'w') as f:  # doctest: +SKIP
+   ...     f.write(estimator_html_repr(clf))
+
 .. topic:: Examples:
 
  * :ref:`sphx_glr_auto_examples_compose_plot_column_transformer.py`

diff --git a/doc/whats_new/v0.23.rst b/doc/whats_new/v0.23.rst
@@ -567,6 +567,9 @@ Changelog
 :mod:`sklearn.utils`
 ....................
 
+- |Feature| Adds :func:`utils.estimator_html_repr` for returning a
+  HTML representation of an estimator. :pr:`14180` by `Thomas Fan`_.
+
 - |Enhancement| improve error message in :func:`utils.validation.column_or_1d`.
   :pr:`15926` by :user:`Loïc Estève <lesteve>`.
 
@@ -605,6 +608,11 @@ Changelog
 Miscellaneous
 .............
 
+- |MajorFeature| Adds a HTML representation of estimators to be shown in
+  a jupyter notebook or lab. This visualization is acitivated by setting the
+  `display` option in :func:`sklearn.set_config`. :pr:`14180` by
+  `Thomas Fan`_.
+
 - |Enhancement| ``scikit-learn`` now works with ``mypy`` without errors.
   :pr:`16726` by `Roman Yurchak`_.
 

diff --git a/examples/compose/plot_column_transformer_mixed_types.py b/examples/compose/plot_column_transformer_mixed_types.py
@@ -87,6 +87,15 @@
 clf.fit(X_train, y_train)
 print("model score: %.3f" % clf.score(X_test, y_test))
 
+##############################################################################
+# HTML representation of ``Pipeline``
+###############################################################################
+# When the ``Pipeline`` is printed out in a jupyter notebook an HTML
+# representation of the estimator is displayed as follows:
+from sklearn import set_config
+set_config(display='diagram')
+clf
+
 ###############################################################################
 # Use ``ColumnTransformer`` by selecting column by data types
 ###############################################################################

diff --git a/sklearn/_config.py b/sklearn/_config.py
@@ -7,6 +7,7 @@
     'assume_finite': bool(os.environ.get('SKLEARN_ASSUME_FINITE', False)),
     'working_memory': int(os.environ.get('SKLEARN_WORKING_MEMORY', 1024)),
     'print_changed_only': True,
+    'display': 'text',
 }
 
 
@@ -27,7 +28,7 @@ def get_config():
 
 
 def set_config(assume_finite=None, working_memory=None,
-               print_changed_only=None):
+               print_changed_only=None, display=None):
     """Set global scikit-learn configuration
 
     .. versionadded:: 0.19
@@ -59,6 +60,13 @@ def set_config(assume_finite=None, working_memory=None,
 
         .. versionadded:: 0.21
 
+    display : {'text', 'diagram'}, optional
+        If 'diagram', estimators will be displayed as text in a jupyter lab
+        of notebook context. If 'text', estimators will be displayed as
+        text. Default is 'text'.
+
+        .. versionadded:: 0.23
+
     See Also
     --------
     config_context: Context manager for global scikit-learn configuration
@@ -70,6 +78,8 @@ def set_config(assume_finite=None, working_memory=None,
         _global_config['working_memory'] = working_memory
     if print_changed_only is not None:
         _global_config['print_changed_only'] = print_changed_only
+    if display is not None:
+        _global_config['display'] = display
 
 
 @contextmanager
@@ -100,6 +110,13 @@ def config_context(**new_config):
         .. versionchanged:: 0.23
            Default changed from False to True.
 
+    display : {'text', 'diagram'}, optional
+        If 'diagram', estimators will be displayed as text in a jupyter lab
+        of notebook context. If 'text', estimators will be displayed as
+        text. Default is 'text'.
+
+        .. versionadded:: 0.23
+
     Notes
     -----
     All settings, not just those presently modified, will be returned to

diff --git a/sklearn/base.py b/sklearn/base.py
@@ -17,9 +17,11 @@
 import numpy as np
 
 from . import __version__
+from ._config import get_config
 from .utils import _IS_32BIT
 from .utils.validation import check_X_y
 from .utils.validation import check_array
+from .utils._estimator_html_repr import estimator_html_repr
 from .utils.validation import _deprecate_positional_args
 
 _DEFAULT_TAGS = {
@@ -435,6 +437,17 @@ def _validate_data(self, X, y=None, reset=True,
 
         return out
 
+    def _repr_html_(self):
+        """HTML representation of estimator"""
+        return estimator_html_repr(self)
+
+    def _repr_mimebundle_(self, **kwargs):
+        """Mime bundle used by jupyter kernels to display estimator"""
+        output = {"text/plain": repr(self)}
+        if get_config()["display"] == 'diagram':
+            output["text/html"] = estimator_html_repr(self)
+        return output
+
 
 class ClassifierMixin:
     """Mixin class for all classifiers in scikit-learn."""

diff --git a/sklearn/compose/_column_transformer.py b/sklearn/compose/_column_transformer.py
@@ -15,6 +15,7 @@
 from joblib import Parallel, delayed
 
 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
@@ -637,6 +638,11 @@ def _hstack(self, Xs):
             Xs = [f.toarray() if sparse.issparse(f) else f for f in Xs]
             return np.hstack(Xs)
 
+    def _sk_visual_block_(self):
+        names, transformers, name_details = zip(*self.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"""

diff --git a/sklearn/ensemble/_stacking.py b/sklearn/ensemble/_stacking.py
@@ -13,6 +13,7 @@
 from ..base import clone
 from ..base import ClassifierMixin, RegressorMixin, TransformerMixin
 from ..base import is_classifier, is_regressor
+from ..utils._estimator_html_repr import _VisualBlock
 
 from ._base import _fit_single_estimator
 from ._base import _BaseHeterogeneousEnsemble
@@ -233,6 +234,14 @@ def predict(self, X, **predict_params):
             self.transform(X), **predict_params
         )
 
+    def _sk_visual_block_(self, final_estimator):
+        names, estimators = zip(*self.estimators)
+        parallel = _VisualBlock('parallel', estimators, names=names,
+                                dash_wrapped=False)
+        serial = _VisualBlock('serial', (parallel, final_estimator),
+                              dash_wrapped=False)
+        return _VisualBlock('serial', [serial])
+
 
 class StackingClassifier(ClassifierMixin, _BaseStacking):
     """Stack of estimators with a final classifier.
@@ -496,6 +505,15 @@ def transform(self, X):
         """
         return self._transform(X)
 
+    def _sk_visual_block_(self):
+        # If final_estimator's default changes then this should be
+        # updated.
+        if self.final_estimator is None:
+            final_estimator = LogisticRegression()
+        else:
+            final_estimator = self.final_estimator
+        return super()._sk_visual_block_(final_estimator)
+
 
 class StackingRegressor(RegressorMixin, _BaseStacking):
     """Stack of estimators with a final regressor.
@@ -665,3 +683,12 @@ def transform(self, X):
             Prediction outputs for each estimator.
         """
         return self._transform(X)
+
+    def _sk_visual_block_(self):
+        # If final_estimator's default changes then this should be
+        # updated.
+        if self.final_estimator is None:
+            final_estimator = RidgeCV()
+        else:
+            final_estimator = self.final_estimator
+        return super()._sk_visual_block_(final_estimator)
diff --git a/sklearn/ensemble/_voting.py b/sklearn/ensemble/_voting.py
@@ -32,6 +32,7 @@
 from ..utils.validation import column_or_1d
 from ..utils.validation import _deprecate_positional_args
 from ..exceptions import NotFittedError
+from ..utils._estimator_html_repr import _VisualBlock
 
 
 class _BaseVoting(TransformerMixin, _BaseHeterogeneousEnsemble):
@@ -104,6 +105,10 @@ def n_features_in_(self):
 
         return self.estimators_[0].n_features_in_
 
+    def _sk_visual_block_(self):
+        names, estimators = zip(*self.estimators)
+        return _VisualBlock('parallel', estimators, names=names)
+
 
 class VotingClassifier(ClassifierMixin, _BaseVoting):
     """Soft Voting/Majority Rule classifier for unfitted estimators.

diff --git a/sklearn/pipeline.py b/sklearn/pipeline.py
@@ -18,6 +18,7 @@
 from joblib import Parallel, delayed
 
 from .base import clone, TransformerMixin
+from .utils._estimator_html_repr import _VisualBlock
 from .utils.metaestimators import if_delegate_has_method
 from .utils import Bunch, _print_elapsed_time
 from .utils.validation import check_memory
@@ -623,6 +624,21 @@ def n_features_in_(self):
         # delegate to first step (which will call _check_is_fitted)
         return self.steps[0][1].n_features_in_
 
+    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."""
@@ -1004,6 +1020,10 @@ def n_features_in_(self):
         # X is passed to all transformers so we just delegate to the first one
         return self.transformer_list[0][1].n_features_in_
 
+    def _sk_visual_block_(self):
+        names, transformers = zip(*self.transformer_list)
+        return _VisualBlock('parallel', transformers, names=names)
+
 
 def make_union(*transformers, **kwargs):
     """

diff --git a/sklearn/tests/test_base.py b/sklearn/tests/test_base.py
@@ -23,6 +23,7 @@
 
 from sklearn.base import TransformerMixin
 from sklearn.utils._mocking import MockDataFrame
+from sklearn import config_context
 import pickle
 
 
@@ -511,3 +512,16 @@ def fit(self, X, y=None):
         params = est.get_params()
 
     assert params['param'] is None
+
+
+def test_repr_mimebundle_():
+    # Checks the display configuration flag controls the json output
+    tree = DecisionTreeClassifier()
+    output = tree._repr_mimebundle_()
+    assert "text/plain" in output
+    assert "text/html" not in output
+
+    with config_context(display='diagram'):
+        output = tree._repr_mimebundle_()
+        assert "text/plain" in output
+        assert "text/html" in output
diff --git a/sklearn/tests/test_config.py b/sklearn/tests/test_config.py
@@ -4,15 +4,17 @@
 
 def test_config_context():
     assert get_config() == {'assume_finite': False, 'working_memory': 1024,
-                            'print_changed_only': True}
+                            'print_changed_only': True,
+                            'display': 'text'}
 
     # Not using as a context manager affects nothing
     config_context(assume_finite=True)
     assert get_config()['assume_finite'] is False
 
     with config_context(assume_finite=True):
         assert get_config() == {'assume_finite': True, 'working_memory': 1024,
-                                'print_changed_only': True}
+                                'print_changed_only': True,
+                                'display': 'text'}
     assert get_config()['assume_finite'] is False
 
     with config_context(assume_finite=True):
@@ -37,7 +39,8 @@ def test_config_context():
         assert get_config()['assume_finite'] is True
 
     assert get_config() == {'assume_finite': False, 'working_memory': 1024,
-                            'print_changed_only': True}
+                            'print_changed_only': True,
+                            'display': 'text'}
 
     # No positional arguments
     assert_raises(TypeError, config_context, True)

diff --git a/sklearn/utils/__init__.py b/sklearn/utils/__init__.py
@@ -25,6 +25,7 @@
 from ..exceptions import DataConversionWarning
 from .deprecation import deprecated
 from .fixes import np_version
+from ._estimator_html_repr import estimator_html_repr
 from .validation import (as_float_array,
                          assert_all_finite,
                          check_random_state, column_or_1d, check_array,
@@ -52,7 +53,7 @@
            "check_symmetric", "indices_to_mask", "deprecated",
            "parallel_backend", "register_parallel_backend",
            "resample", "shuffle", "check_matplotlib_support", "all_estimators",
-           "DataConversionWarning"
+           "DataConversionWarning", "estimator_html_repr"
            ]
 
 IS_PYPY = platform.python_implementation() == 'PyPy'