DOC: make it explicit that groups is used to perform the split in GridSearch CV (scikit-learn#29939)

victoris93 · web-flow · commit 783d72f76d03 · 2024-09-27T19:39:04.000+02:00
diff --git a/sklearn/model_selection/_search.py b/sklearn/model_selection/_search.py
@@ -906,9 +906,13 @@ def fit(self, X, y=None, **params):
             and the CV splitter.
 
             If a fit parameter is an array-like whose length is equal to
-            `num_samples` then it will be split across CV groups along with `X`
-            and `y`. For example, the :term:`sample_weight` parameter is split
-            because `len(sample_weights) = len(X)`.
+            `num_samples` then it will be split by cross-validation along with
+            `X` and `y`. For example, the :term:`sample_weight` parameter is
+            split because `len(sample_weights) = len(X)`. However, this behavior
+            does not apply to `groups` which is passed to the splitter configured
+            via the `cv` parameter of the constructor. Thus, `groups` is used
+            *to perform the split* and determines which samples are
+            assigned to the each side of the a split.
 
         Returns
         -------
