Revert "FIX 'MultiTaskLasso' object has no attribute 'coef_' when warm_start = True (scikit-learn#12361)"

Xing · Xing · commit cdcd6bfb3e6e · 2019-04-28T15:16:38.000-04:00
This reverts commit cab496e.
diff --git a/doc/whats_new/v0.21.rst b/doc/whats_new/v0.21.rst
@@ -40,12 +40,6 @@ Support for Python 3.4 and below has been officially dropped.
 - An entry goes here
 - An entry goes here
 
-:mod:`sklearn.linear_model`
-...........................
-- |Fix| Fixed a bug in :class:`linear_model.MultiTaskElasticNet` which was breaking
-  ``MultiTaskElasticNet`` and ``MultiTaskLasso`` when ``warm_start = True``. :issue:`12360`
-  by :user:`Aakanksha Joshi <joaak>`.
-
 :mod:`sklearn.cluster`
 ......................
 
diff --git a/sklearn/linear_model/coordinate_descent.py b/sklearn/linear_model/coordinate_descent.py
@@ -1795,7 +1795,7 @@ def fit(self, X, y):
         X, y, X_offset, y_offset, X_scale = _preprocess_data(
             X, y, self.fit_intercept, self.normalize, copy=False)
 
-        if not self.warm_start or not hasattr(self, "coef_"):
+        if not self.warm_start or self.coef_ is None:
             self.coef_ = np.zeros((n_tasks, n_features), dtype=X.dtype.type,
                                   order='F')
 
diff --git a/sklearn/linear_model/tests/test_coordinate_descent.py b/sklearn/linear_model/tests/test_coordinate_descent.py
@@ -818,15 +818,3 @@ def test_coef_shape_not_zero():
     est_no_intercept = Lasso(fit_intercept=False)
     est_no_intercept.fit(np.c_[np.ones(3)], np.ones(3))
     assert est_no_intercept.coef_.shape == (1,)
-
-
-def test_warm_start_multitask_lasso():
-    X, y, X_test, y_test = build_dataset()
-    Y = np.c_[y, y]
-    clf = MultiTaskLasso(alpha=0.1, max_iter=5, warm_start=True)
-    ignore_warnings(clf.fit)(X, Y)
-    ignore_warnings(clf.fit)(X, Y)  # do a second round with 5 iterations
-
-    clf2 = MultiTaskLasso(alpha=0.1, max_iter=10)
-    ignore_warnings(clf2.fit)(X, Y)
-    assert_array_almost_equal(clf2.coef_, clf.coef_)
