ENH: show warning when np.maximum receives more than 2 inputs

lvllvl · lvllvl · commit 696f11ac3121 · 2025-05-30T01:31:57.000Z
diff --git a/numpy/_core/src/umath/ufunc_object.c b/numpy/_core/src/umath/ufunc_object.c
@@ -88,6 +88,7 @@ typedef struct {
                        provided, then this is NULL. */
 } ufunc_full_args;
 
+extern PyUFuncObject *UFUNC_MAXIMUM;
 
 /* ---------------------------------------------------------------- */
 
@@ -4325,7 +4326,21 @@ ufunc_generic_fastcall(PyUFuncObject *ufunc,
                 ufunc_get_name_cstr(ufunc) , nin, nop, len_args);
         goto fail;
     }
-
+    // 2) Only when there *are* extra pos-args *and* no keywords...
+    if (len_args > nin && (kwnames==NULL || PyTuple_Size(kwnames)==0)) {
+        /* 3) ...then check if it’s the "maximum" ufunc */
+        // if (strcmp(ufunc->name, "maximum") == 0) {
+        if (ufunc == UFUNC_MAXIMUM) {
+            PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
+                "Passing more than 2 positional arguments to np.maximum "
+                "is deprecated; use out=keyword or np.maximum.reduce.");
+            PyErr_Format(PyExc_TypeError,
+                "np.maximum() takes exactly 2 input arguments (%zd given).",
+                len_args);
+            goto fail;
+        }
+    }
+ 
     /* Fetch input arguments. */
     full_args.in = PyArray_TupleFromItems(ufunc->nin, args, 0);
     if (full_args.in == NULL) {
diff --git a/numpy/_core/src/umath/umathmodule.c b/numpy/_core/src/umath/umathmodule.c
@@ -40,6 +40,7 @@
 
 
 static PyUFuncGenericFunction pyfunc_functions[] = {PyUFunc_On_Om};
+PyUFuncObject *UFUNC_MAXIMUM = NULL;
 
 static int
 object_ufunc_type_resolver(PyUFuncObject *ufunc,
@@ -278,6 +279,7 @@ int initumath(PyObject *m)
     if (_PyArray_SetNumericOps(d) < 0) {
         return -1;
     }
+    UFUNC_MAXIMUM = (PyUFuncObject *)PyDict_GetItemString(d, "maximum");
 
     PyDict_SetItemString(d, "conj", s);
     PyDict_SetItemString(d, "mod", s2);
diff --git a/numpy/_core/tests/test_umath.py b/numpy/_core/tests/test_umath.py
@@ -2420,6 +2420,7 @@ def test_strided_array(self):
         assert_equal(np.maximum(arr1[:4:], arr2[::2]), np.array([-2.0, np.nan, 10.0, 1.0]))
         assert_equal(np.maximum(arr1[::3], arr2[:3:]), np.array([-2.0, 0.0, np.nan]))
         assert_equal(np.maximum(arr1[:6:2], arr2[::3], out=out[::3]), np.array([-2.0, 10., np.nan]))
+
         assert_equal(out, out_maxtrue)
 
     def test_precision(self):
@@ -2443,6 +2444,9 @@ def test_precision(self):
                 assert_equal(np.maximum([v1], [v2]), [expected])
                 assert_equal(np.maximum.reduce([v1, v2]), expected)
 
+    def test_maximum_too_many_args(self):
+        with pytest.raises(TypeError, match=r"np\.maximum\(\) takes exactly 2 input arguments \(3 given\)"):
+            np.maximum(1, 2, 3)
 
 class TestMinimum(_FilterInvalids):
     def test_reduce(self):
