[API Compatibility] Support tensor dtype compare using is (#76155)

Author: huangjiyi

paddle/fluid/pybind/eager_utils.cc

@@ -1205,9 +1205,14 @@ PyObject* ToPyObject(const phi::DenseTensor* value) {
 }
 
 PyObject* ToPyObject(const phi::DataType& dtype) {
-  auto obj = ::pybind11::cast(dtype);
-  obj.inc_ref();
-  return obj.ptr();
+  static const std::vector<std::string> dtype_names = {
+      "UNDEFINED", "BOOL",     "UINT8",         "INT8",        "UINT16",
+      "INT16",     "UINT32",   "INT32",         "UINT64",      "INT64",
+      "FLOAT32",   "FLOAT64",  "COMPLEX64",     "COMPLEX128",  "PSTRING",
+      "FLOAT16",   "BFLOAT16", "FLOAT8_E4M3FN", "FLOAT8_E5M2",
+  };
+  return PyObject_GetAttrString(reinterpret_cast<PyObject*>(g_data_type_pytype),
+                                dtype_names[static_cast<int>(dtype)].c_str());
 }
 
 PyObject* ToPyObject(const std::vector<phi::DataType>& dtypes) {

test/legacy_test/test_eager_tensor.py

@@ -1346,6 +1346,20 @@ def test_print_tensor_dtype(self):
 
         self.assertEqual(a_str, expected)
 
+    def test_tensor_dtype_compare(self):
+        a = paddle.randn([2], dtype="float32")
+        b = paddle.randn([2], dtype="float32")
+        c = paddle.randn([2], dtype="float64")
+
+        self.assertTrue(a.dtype == paddle.float32)
+        self.assertTrue(a.dtype == b.dtype)
+        self.assertTrue(a.dtype != paddle.float64)
+        self.assertTrue(a.dtype != c.dtype)
+        self.assertTrue(a.dtype is paddle.float32)
+        self.assertTrue(a.dtype is b.dtype)
+        self.assertTrue(a.dtype is not paddle.float64)
+        self.assertTrue(a.dtype is not c.dtype)
+
     def test___cuda_array_interface__(self):
         """test Tensor.__cuda_array_interface__"""
         with dygraph_guard():