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

lvllvl · lvllvl · commit e4d6fa4538ef · 2025-05-29T21:23:22.000Z
diff --git a/numpy/_core/src/umath/ufunc_object.c b/numpy/_core/src/umath/ufunc_object.c
@@ -4316,20 +4316,27 @@ ufunc_generic_fastcall(PyUFuncObject *ufunc,
      * Outputs and inputs are stored in `full_args.in` and `full_args.out`
      * as tuples (or NULL when no outputs are passed).
      */
-
     /* Check number of arguments */
-    if (NPY_UNLIKELY((len_args < nin) || (len_args > nop))) {
+    // 1 Bounds check: common case, fails quickly
+    if (NPY_UNLIKELY(len_args < nin) || (len_args > nop)) {
         PyErr_Format(PyExc_TypeError,
-                "%s() takes from %d to %d positional arguments but "
-                "%zd were given",
-                ufunc_get_name_cstr(ufunc) , nin, nop, len_args);
+            "%s() takes from %d to %d positional arguments by %zd were given",
+            ufunc_get_name_cstr(ufunc), nin, nop, len_args);
         goto fail;
     }
-
-    /* Fetch input arguments. */
-    full_args.in = PyArray_TupleFromItems(ufunc->nin, args, 0);
-    if (full_args.in == NULL) {
-        goto fail;
+    
+    // 2 Only when there are extra pos args and no keywords
+    if (len_args > nin && (kwnames==NULL || PyTuple_Size(kwnames)==0)) {
+        // 3 Check if it's the maximum ufunc
+        if (strcmp(ufunc->name, "maximum") == 0) {
+            PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
+                "Passing more than 2 positional arguments to np.maximum "
+                "is deprecaated; use out=keywords or np.maximum.reduce.");
+            PyErr_Format(PyExc_TypeError,
+                "np.maximum() takes exactly 2 input arguments (%zd given).",
+                len_args);
+            goto fail;
+        }
     }
 
     /*
@@ -4598,12 +4605,12 @@ static PyObject *
 ufunc_generic_vectorcall(PyObject *ufunc,
         PyObject *const *args, size_t len_args, PyObject *kwnames)
 {
-    /*
-     * Unlike METH_FASTCALL, `len_args` may have a flag to signal that
-     * args[-1] may be (temporarily) used. So normalize it here.
-     */
-    return ufunc_generic_fastcall((PyUFuncObject *)ufunc,
-            args, PyVectorcall_NARGS(len_args), kwnames, NPY_FALSE);
+    return ufunc_generic_fastcall(
+            (PyUFuncObject *)ufunc,
+            args,
+            PyVectorcall_NARGS(len_args),
+            kwnames,
+            NPY_FALSE);
 }
 
 
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):
