Merge pull request #474 from aldanor/feature/numpy-dtype-ex

Overriding field names when binding structured dtypes

include/pybind11/numpy.h

@@ -20,6 +20,7 @@
 #include <string>
 #include <initializer_list>
 #include <functional>
+#include <utility>
 
 #if defined(_MSC_VER)
 #  pragma warning(push)
@@ -748,14 +749,16 @@ std::string npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>>::form
 template <typename T>
 PyObject* npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>>::dtype_ptr = nullptr;
 
-// Extract name, offset and format descriptor for a struct field
-#define PYBIND11_FIELD_DESCRIPTOR(Type, Field) \
-    ::pybind11::detail::field_descriptor { \
-        #Field, offsetof(Type, Field), sizeof(decltype(static_cast<Type*>(0)->Field)), \
-        ::pybind11::format_descriptor<decltype(static_cast<Type*>(0)->Field)>::format(), \
-        ::pybind11::detail::npy_format_descriptor<decltype(static_cast<Type*>(0)->Field)>::dtype() \
+#define PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, Name)                                          \
+    ::pybind11::detail::field_descriptor {                                                    \
+        Name, offsetof(T, Field), sizeof(decltype(std::declval<T>().Field)),                  \
+        ::pybind11::format_descriptor<decltype(std::declval<T>().Field)>::format(),           \
+        ::pybind11::detail::npy_format_descriptor<decltype(std::declval<T>().Field)>::dtype() \
     }
 
+// Extract name, offset and format descriptor for a struct field
+#define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
+
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
 #define PYBIND11_EVAL0(...) __VA_ARGS__
@@ -792,6 +795,27 @@ PyObject* npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>>::dtype_
     ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
         ({PYBIND11_MAP_LIST (PYBIND11_FIELD_DESCRIPTOR, Type, __VA_ARGS__)})
 
+#ifdef _MSC_VER
+#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
+    PYBIND11_EVAL0 (PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0))
+#else
+#define PYBIND11_MAP2_LIST_NEXT1(test, next) \
+    PYBIND11_MAP_NEXT0 (test, PYBIND11_MAP_COMMA next, 0)
+#endif
+#define PYBIND11_MAP2_LIST_NEXT(test, next) \
+    PYBIND11_MAP2_LIST_NEXT1 (PYBIND11_MAP_GET_END test, next)
+#define PYBIND11_MAP2_LIST0(f, t, x1, x2, peek, ...) \
+    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST1) (f, t, peek, __VA_ARGS__)
+#define PYBIND11_MAP2_LIST1(f, t, x1, x2, peek, ...) \
+    f(t, x1, x2) PYBIND11_MAP2_LIST_NEXT (peek, PYBIND11_MAP2_LIST0) (f, t, peek, __VA_ARGS__)
+// PYBIND11_MAP2_LIST(f, t, a1, a2, ...) expands to f(t, a1, a2), f(t, a3, a4), ...
+#define PYBIND11_MAP2_LIST(f, t, ...) \
+    PYBIND11_EVAL (PYBIND11_MAP2_LIST1 (f, t, __VA_ARGS__, (), 0))
+
+#define PYBIND11_NUMPY_DTYPE_EX(Type, ...) \
+    ::pybind11::detail::npy_format_descriptor<Type>::register_dtype \
+        ({PYBIND11_MAP2_LIST (PYBIND11_FIELD_DESCRIPTOR_EX, Type, __VA_ARGS__)})
+
 template  <class T>
 using array_iterator = typename std::add_pointer<T>::type;
 

tests/test_numpy_dtypes.cpp

@@ -67,6 +67,11 @@ struct StringStruct {
     std::array<char, 3> b;
 };
 
+PYBIND11_PACKED(struct StructWithUglyNames {
+    int8_t __x__;
+    uint64_t __y__;
+});
+
 enum class E1 : int64_t { A = -1, B = 1 };
 enum E2 : uint8_t { X = 1, Y = 2 };
 
@@ -197,7 +202,8 @@ py::list print_dtypes() {
         py::dtype::of<PartialStruct>().str(),
         py::dtype::of<PartialNestedStruct>().str(),
         py::dtype::of<StringStruct>().str(),
-        py::dtype::of<EnumStruct>().str()
+        py::dtype::of<EnumStruct>().str(),
+        py::dtype::of<StructWithUglyNames>().str()
     };
     auto l = py::list();
     for (const auto &s : dtypes) {
@@ -312,6 +318,8 @@ test_initializer numpy_dtypes([](py::module &m) {
     // ... or after
     py::class_<PackedStruct>(m, "PackedStruct");
 
+    PYBIND11_NUMPY_DTYPE_EX(StructWithUglyNames, __x__, "x", __y__, "y");
+
     m.def("create_rec_simple", &create_recarray<SimpleStruct>);
     m.def("create_rec_packed", &create_recarray<PackedStruct>);
     m.def("create_rec_nested", &create_nested);

tests/test_numpy_dtypes.py

@@ -42,7 +42,8 @@ def test_dtype():
         "{'names':['x','y','z'], 'formats':['?','<u4','<f4'], 'offsets':[0,4,8], 'itemsize':24}",
         "{'names':['a'], 'formats':[{'names':['x','y','z'], 'formats':['?','<u4','<f4'], 'offsets':[0,4,8], 'itemsize':24}], 'offsets':[8], 'itemsize':40}",
         "[('a', 'S3'), ('b', 'S3')]",
-        "[('e1', '<i8'), ('e2', 'u1')]"
+        "[('e1', '<i8'), ('e2', 'u1')]",
+        "[('x', 'i1'), ('y', '<u8')]"
     ]
 
     d1 = np.dtype({'names': ['a', 'b'], 'formats': ['int32', 'float64'],