Merge pull request #13328 from eric-wieser/fix-weird-reduce-logic

MAINT: Tidy up error message for accumulate and reduceat

1 files changed, 27 insertions, 25 deletions

diff --git a/numpy/core/src/umath/ufunc_object.c b/numpy/core/src/umath/ufunc_object.c
index 6a96fe296..dd5fb7e03 100644
--- a/numpy/core/src/umath/ufunc_object.c
+++ b/numpy/core/src/umath/ufunc_object.c
@@ -4535,11 +4535,17 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc, PyObject *args,
 
     /* Convert the 'axis' parameter into a list of axes */
     if (axes_in == NULL) {
-        naxes = 1;
-        axes[0] = 0;
+        /* apply defaults */
+        if (ndim == 0) {
+            naxes = 0;
+        }
+        else {
+            naxes = 1;
+            axes[0] = 0;
+        }
     }
-    /* Convert 'None' into all the axes */
     else if (axes_in == Py_None) {
+        /* Convert 'None' into all the axes */
         naxes = ndim;
         for (i = 0; i < naxes; ++i) {
             axes[i] = i;
@@ -4564,40 +4570,28 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc, PyObject *args,
             axes[i] = (int)axis;
         }
     }
-    /* Try to interpret axis as an integer */
     else {
+        /* Try to interpret axis as an integer */
         int axis = PyArray_PyIntAsInt(axes_in);
         /* TODO: PyNumber_Index would be good to use here */
         if (error_converting(axis)) {
             goto fail;
         }
-        /* Special case letting axis={0 or -1} slip through for scalars */
-        if (ndim == 0 && (axis == 0 || axis == -1)) {
-            axis = 0;
-        }
-        else if (check_and_adjust_axis(&axis, ndim) < 0) {
-            goto fail;
-        }
-        axes[0] = (int)axis;
-        naxes = 1;
-    }
-
-    /* Check to see if input is zero-dimensional. */
-    if (ndim == 0) {
         /*
-         * A reduction with no axes is still valid but trivial.
          * As a special case for backwards compatibility in 'sum',
-         * 'prod', et al, also allow a reduction where axis=0, even
+         * 'prod', et al, also allow a reduction for scalars even
          * though this is technically incorrect.
          */
-        naxes = 0;
-
-        if (!(operation == UFUNC_REDUCE &&
-                    (naxes == 0 || (naxes == 1 && axes[0] == 0)))) {
-            PyErr_Format(PyExc_TypeError, "cannot %s on a scalar",
-                         _reduce_type[operation]);
+        if (ndim == 0 && (axis == 0 || axis == -1)) {
+            naxes = 0;
+        }
+        else if (check_and_adjust_axis(&axis, ndim) < 0) {
             goto fail;
         }
+        else {
+            axes[0] = (int)axis;
+            naxes = 1;
+        }
     }
 
      /*
@@ -4640,6 +4634,10 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc, PyObject *args,
         Py_XDECREF(wheremask);
         break;
     case UFUNC_ACCUMULATE:
+        if (ndim == 0) {
+            PyErr_SetString(PyExc_TypeError, "cannot accumulate on a scalar");
+            goto fail;
+        }
         if (naxes != 1) {
             PyErr_SetString(PyExc_ValueError,
                         "accumulate does not allow multiple axes");
@@ -4649,6 +4647,10 @@ PyUFunc_GenericReduction(PyUFuncObject *ufunc, PyObject *args,
                                                   otype->type_num);
         break;
     case UFUNC_REDUCEAT:
+        if (ndim == 0) {
+            PyErr_SetString(PyExc_TypeError, "cannot reduceat on a scalar");
+            goto fail;
+        }
         if (naxes != 1) {
             PyErr_SetString(PyExc_ValueError,
                         "reduceat does not allow multiple axes");