Convert multiarray to multi-phase init (PEP 489)

numpy · seberg · May 29, 2025 · May 21, 2025 · May 29, 2025 · d4b3f9bddf8cc1fe32f056a51e29f27ec0bdfea6
commit d4b3f9bddf8cc1fe32f056a51e29f27ec0bdfea6
diff --git a/numpy/_core/__init__.py b/numpy/_core/__init__.py
@@ -23,6 +23,10 @@
 except ImportError as exc:
     import sys
 
+    # Bypass for the module re-initialization opt-out
+    if exc.msg == "cannot load module more than once per process":
+        raise
+
     # Basically always, the problem should be that the C module is wrong/missing...
     if (
         isinstance(exc, ModuleNotFoundError)

diff --git a/numpy/_core/src/multiarray/_multiarray_tests.c.src b/numpy/_core/src/multiarray/_multiarray_tests.c.src
@@ -2413,41 +2413,56 @@ static PyMethodDef Multiarray_TestsMethods[] = {
 };
 
 
-static struct PyModuleDef moduledef = {
-        PyModuleDef_HEAD_INIT,
-        "_multiarray_tests",
-        NULL,
-        -1,
-        Multiarray_TestsMethods,
-        NULL,
-        NULL,
-        NULL,
-        NULL
-};
+static int module_loaded = 0;
 
-PyMODINIT_FUNC PyInit__multiarray_tests(void)
+static int
+_multiarray_tests_exec(PyObject *m)
 {
-    PyObject *m;
+    // https://docs.python.org/3/howto/isolating-extensions.html#opt-out-limiting-to-one-module-object-per-process
+    if (module_loaded) {
+        PyErr_SetString(PyExc_ImportError,
+                        "cannot load module more than once per process");
+        return -1;
+    }
+    module_loaded = 1;
 
-    m = PyModule_Create(&moduledef);
-    if (m == NULL) {
-        return m;
+    if (PyArray_ImportNumPyAPI() < 0) {
+        return -1;
     }
-    import_array();
     if (init_argparse_mutex() < 0) {
-        return NULL;
+        return -1;
     }
     if (PyErr_Occurred()) {
         PyErr_SetString(PyExc_RuntimeError,
                         "cannot load _multiarray_tests module.");
     }
 
-#if Py_GIL_DISABLED
-    // signal this module supports running with the GIL disabled
-    PyUnstable_Module_SetGIL(m, Py_MOD_GIL_NOT_USED);
+    return 0;
+}
+
+static struct PyModuleDef_Slot _multiarray_tests_slots[] = {
+    {Py_mod_exec, _multiarray_tests_exec},
+#if PY_VERSION_HEX >= 0x030c00f0  // Python 3.12+
+    {Py_mod_multiple_interpreters, Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED},
+#endif
+#if PY_VERSION_HEX >= 0x030d00f0  // Python 3.13+
+    // signal that this module supports running without an active GIL
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
 #endif
+    {0, NULL},
+};
+
+static struct PyModuleDef moduledef = {
+    .m_base = PyModuleDef_HEAD_INIT,
+    .m_name = "_multiarray_tests",
+    .m_size = 0,
+    .m_methods = Multiarray_TestsMethods,
+    .m_slots = _multiarray_tests_slots,
+};
 
-    return m;
+PyMODINIT_FUNC PyInit__multiarray_tests(void)
+{
+    return PyModuleDef_Init(&moduledef);
 }
 
 NPY_NO_EXPORT int