ENH Improves error message for mixed types for feature names (#25018)

Co-authored-by: jeremie du boisberranger <jeremiedbb@yahoo.fr>

sklearn/tests/test_base.py

@@ -651,8 +651,12 @@ def transform(self, X):
     df_mixed = pd.DataFrame(X_np, columns=["a", "b", 1, 2])
     trans = NoOpTransformer()
     msg = re.escape(
-        "Feature names only support names that are all strings. "
-        "Got feature names with dtypes: ['int', 'str']"
+        "Feature names are only supported if all input features have string names, "
+        "but your input has ['int', 'str'] as feature name / column name types. "
+        "If you want feature names to be stored and validated, you must convert "
+        "them all to strings, by using X.columns = X.columns.astype(str) for "
+        "example. Otherwise you can remove feature / column names from your input "
+        "data, or convert them all to a non-string data type."
     )
     with pytest.raises(TypeError, match=msg):
         trans.fit(df_mixed)

sklearn/utils/tests/test_validation.py

@@ -1675,8 +1675,12 @@ def test_get_feature_names_invalid_dtypes(names, dtypes):
     X = pd.DataFrame([[1, 2], [4, 5], [5, 6]], columns=names)
 
     msg = re.escape(
-        "Feature names only support names that are all strings. "
-        f"Got feature names with dtypes: {dtypes}."
+        "Feature names are only supported if all input features have string names, "
+        f"but your input has {dtypes} as feature name / column name types. "
+        "If you want feature names to be stored and validated, you must convert "
+        "them all to strings, by using X.columns = X.columns.astype(str) for "
+        "example. Otherwise you can remove feature / column names from your input "
+        "data, or convert them all to a non-string data type."
     )
     with pytest.raises(TypeError, match=msg):
         names = _get_feature_names(X)

sklearn/utils/validation.py

@@ -1884,8 +1884,12 @@ def _get_feature_names(X):
     # mixed type of string and non-string is not supported
     if len(types) > 1 and "str" in types:
         raise TypeError(
-            "Feature names only support names that are all strings. "
-            f"Got feature names with dtypes: {types}."
+            "Feature names are only supported if all input features have string names, "
+            f"but your input has {types} as feature name / column name types. "
+            "If you want feature names to be stored and validated, you must convert "
+            "them all to strings, by using X.columns = X.columns.astype(str) for "
+            "example. Otherwise you can remove feature / column names from your input "
+            "data, or convert them all to a non-string data type."
         )
 
     # Only feature names of all strings are supported