Rework warning in check_array when silent convert string to float (scikit-learn#11577)

Author: massich

sklearn/utils/tests/test_validation.py

@@ -291,40 +291,17 @@ def test_check_array():
     assert_true(isinstance(result, np.ndarray))
 
     # deprecation warning if string-like array with dtype="numeric"
-    X_str = [['a', 'b'], ['c', 'd']]
-    assert_warns_message(
-        FutureWarning,
-        "arrays of strings will be interpreted as decimal numbers if "
-        "parameter 'dtype' is 'numeric'. It is recommended that you convert "
-        "the array to type np.float64 before passing it to check_array.",
-        check_array, X_str, "numeric")
-    assert_warns_message(
-        FutureWarning,
-        "arrays of strings will be interpreted as decimal numbers if "
-        "parameter 'dtype' is 'numeric'. It is recommended that you convert "
-        "the array to type np.float64 before passing it to check_array.",
-        check_array, np.array(X_str, dtype='U'), "numeric")
-    assert_warns_message(
-        FutureWarning,
-        "arrays of strings will be interpreted as decimal numbers if "
-        "parameter 'dtype' is 'numeric'. It is recommended that you convert "
-        "the array to type np.float64 before passing it to check_array.",
-        check_array, np.array(X_str, dtype='S'), "numeric")
+    expected_warn_regex = r"converted to decimal numbers if dtype='numeric'"
+    X_str = [['11', '12'], ['13', 'xx']]
+    for X in [X_str, np.array(X_str, dtype='U'), np.array(X_str, dtype='S')]:
+        with pytest.warns(FutureWarning, match=expected_warn_regex):
+            check_array(X, dtype="numeric")
 
     # deprecation warning if byte-like array with dtype="numeric"
     X_bytes = [[b'a', b'b'], [b'c', b'd']]
-    assert_warns_message(
-        FutureWarning,
-        "arrays of strings will be interpreted as decimal numbers if "
-        "parameter 'dtype' is 'numeric'. It is recommended that you convert "
-        "the array to type np.float64 before passing it to check_array.",
-        check_array, X_bytes, "numeric")
-    assert_warns_message(
-        FutureWarning,
-        "arrays of strings will be interpreted as decimal numbers if "
-        "parameter 'dtype' is 'numeric'. It is recommended that you convert "
-        "the array to type np.float64 before passing it to check_array.",
-        check_array, np.array(X_bytes, dtype='V1'), "numeric")
+    for X in [X_bytes, np.array(X_bytes, dtype='V1')]:
+        with pytest.warns(FutureWarning, match=expected_warn_regex):
+            check_array(X, dtype="numeric")
 
 
 def test_check_array_pandas_dtype_object_conversion():

sklearn/utils/validation.py

@@ -546,10 +546,12 @@ def check_array(array, accept_sparse=False, accept_large_sparse=True,
         # in the future np.flexible dtypes will be handled like object dtypes
         if dtype_numeric and np.issubdtype(array.dtype, np.flexible):
             warnings.warn(
-                "Beginning in version 0.22, arrays of strings will be "
-                "interpreted as decimal numbers if parameter 'dtype' is "
-                "'numeric'. It is recommended that you convert the array to "
-                "type np.float64 before passing it to check_array.",
+                "Beginning in version 0.22, arrays of bytes/strings will be "
+                "converted to decimal numbers if dtype='numeric'. "
+                "It is recommended that you convert the array to "
+                "a float dtype before using it in scikit-learn, "
+                "for example by using "
+                "your_array = your_array.astype(np.float64).",
                 FutureWarning)
 
         # make sure we actually converted to numeric: