MAINT: Include `numpy._core` imports (#4857)

* MAINT: Include numpy._core imports

* style: pre-commit fixes

* Apply review comments

* style: pre-commit fixes

* Add no-inline attribute

* Select submodule name based on numpy version

* style: pre-commit fixes

* Update pre-commit check

* Add error_already_set and simplify if statement

* Update .pre-commit-config.yaml

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgkio@gmail.com>

.pre-commit-config.yaml

@@ -142,7 +142,7 @@ repos:
   - id: disallow-caps
     name: Disallow improper capitalization
     language: pygrep
-    entry: PyBind|Numpy|Cmake|CCache|PyTest
+    entry: PyBind|\bNumpy\b|Cmake|CCache|PyTest
     exclude: ^\.pre-commit-config.yaml$
 
 # PyLint has native support - not always usable, but works for us

include/pybind11/numpy.h

@@ -120,6 +120,20 @@ inline numpy_internals &get_numpy_internals() {
     return *ptr;
 }
 
+PYBIND11_NOINLINE module_ import_numpy_core_submodule(const char *submodule_name) {
+    module_ numpy = module_::import("numpy");
+    str version_string = numpy.attr("__version__");
+
+    module_ numpy_lib = module_::import("numpy.lib");
+    object numpy_version = numpy_lib.attr("NumpyVersion")(version_string);
+    int major_version = numpy_version.attr("major").cast<int>();
+
+    /* `numpy.core` was renamed to `numpy._core` in NumPy 2.0 as it officially
+        became a private module. */
+    std::string numpy_core_path = major_version >= 2 ? "numpy._core" : "numpy.core";
+    return module_::import((numpy_core_path + "." + submodule_name).c_str());
+}
+
 template <typename T>
 struct same_size {
     template <typename U>
@@ -263,9 +277,13 @@ private:
     };
 
     static npy_api lookup() {
-        module_ m = module_::import("numpy.core.multiarray");
+        module_ m = detail::import_numpy_core_submodule("multiarray");
         auto c = m.attr("_ARRAY_API");
         void **api_ptr = (void **) PyCapsule_GetPointer(c.ptr(), nullptr);
+        if (api_ptr == nullptr) {
+            raise_from(PyExc_SystemError, "FAILURE obtaining numpy _ARRAY_API pointer.");
+            throw error_already_set();
+        }
         npy_api api;
 #define DECL_NPY_API(Func) api.Func##_ = (decltype(api.Func##_)) api_ptr[API_##Func];
         DECL_NPY_API(PyArray_GetNDArrayCFeatureVersion);
@@ -626,11 +644,8 @@ public:
 
 private:
     static object _dtype_from_pep3118() {
-        static PyObject *obj = module_::import("numpy.core._internal")
-                                   .attr("_dtype_from_pep3118")
-                                   .cast<object>()
-                                   .release()
-                                   .ptr();
+        module_ m = detail::import_numpy_core_submodule("_internal");
+        static PyObject *obj = m.attr("_dtype_from_pep3118").cast<object>().release().ptr();
         return reinterpret_borrow<object>(obj);
     }