[dtype]: add type() method to access type attribute of PyArray_Descr (eq. to dtype.char in Python)

Author: Bertrand MICHEL

include/pybind11/numpy.h

@@ -507,11 +507,16 @@ class dtype : public object {
         return detail::array_descriptor_proxy(m_ptr)->names != nullptr;
     }
 
-    /// Single-character type code.
+    /// Single-character for dtype's kind (ex: float and double are 'f' or int and long int are 'i')
     char kind() const {
         return detail::array_descriptor_proxy(m_ptr)->kind;
     }
 
+    /// Single-character for dtype's type (ex: float is 'f' and double 'd')
+    char type() const {
+        return detail::array_descriptor_proxy(m_ptr)->type;
+    }
+
 private:
     static object _dtype_from_pep3118() {
         static PyObject *obj = module_::import("numpy.core._internal")

tests/test_numpy_dtypes.cpp

@@ -251,6 +251,38 @@ py::list test_dtype_ctors() {
     return list;
 }
 
+py::list test_dtype_kind() {
+    py::list list;
+    for (auto& dt : {
+                     py::dtype("bool8"),   // bool
+                     py::dtype("int16"),   // short
+                     py::dtype("int32"),   // int
+                     py::dtype("int64"),   // long int
+                     py::dtype("float32"), // float
+                     py::dtype("float64"), // double
+                     py::dtype("float128") // long double
+                    }) {
+        list.append(dt.kind());
+    }
+    return list;
+}
+
+py::list test_dtype_type() {
+    py::list list;
+    for (auto& dt : {
+                     py::dtype("bool8"),   // bool
+                     py::dtype("int16"),   // short
+                     py::dtype("int32"),   // int
+                     py::dtype("int64"),   // long int
+                     py::dtype("float32"), // float
+                     py::dtype("float64"), // double
+                     py::dtype("float128") // long double
+                    }) {
+        list.append(dt.type());
+    }
+    return list;
+}
+
 struct A {};
 struct B {};
 
@@ -376,6 +408,8 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         return l;
     });
     m.def("test_dtype_ctors", &test_dtype_ctors);
+    m.def("test_dtype_kind", &test_dtype_kind);
+    m.def("test_dtype_type", &test_dtype_type);
     m.def("test_dtype_methods", []() {
         py::list list;
         auto dt1 = py::dtype::of<int32_t>();

tests/test_numpy_dtypes.py

@@ -169,6 +169,12 @@ def test_dtype(simple_dtype):
         np.zeros(1, m.trailing_padding_dtype())
     )
 
+    # for dt in m.test_dtype_kind():
+    #     print("dt = ",dt)
+    assert m.test_dtype_kind() == ['b'] + ['i']*3 + ['f']*3
+    assert m.test_dtype_type() == ['?', 'h', 'i', 'l', 'f', 'd', 'g']
+    # assert False
+
 
 def test_recarray(simple_dtype, packed_dtype):
     elements = [(False, 0, 0.0, -0.0), (True, 1, 1.5, -2.5), (False, 2, 3.0, -5.0)]