fix to_tensor bug (#76000) (#76067)

Co-authored-by: wanghuancoder <[email protected]>

Author: zhangbo9674

python/paddle/tensor/creation.py

@@ -713,7 +713,24 @@ def _handle_tensor_dtype(
         if np.isscalar(data) and not isinstance(data, str):
             data = np.array(data)
         elif isinstance(data, (list, tuple)):
-            data = np.array(data)
+            has_tensor = False
+            for d in data:
+                if isinstance(d, paddle.Tensor):
+                    has_tensor = True
+                    break
+            if has_tensor:
+                if (
+                    len(data) == 1
+                    and isinstance(data[0], paddle.Tensor)
+                    and data[0].dtype == paddle.bfloat16
+                ):
+                    data = np.array([data[0].numpy()])
+                else:
+                    data = np.array(data)
+                if not dtype:
+                    dtype = data.dtype
+            else:
+                data = np.array(data)
             if data.dtype == np.object_:
                 raise ValueError(
                     "\n\tFailed to convert input data to a regular ndarray :\n\t - Usually "

test/legacy_test/test_eager_tensor.py

@@ -2129,5 +2129,39 @@ def test_set_dynamic_attribute_to_eager_tensor_instance_create_via_to_pyobject(
         self.assertEqual(tensor_instance.__dict__["_custom_flag"], True)
 
 
+class TestListToTensor(unittest.TestCase):
+    def test_list_to_tensor_bfloat16(self):
+        a = [paddle.to_tensor(2, dtype=paddle.bfloat16)]
+        b = paddle.to_tensor(a)
+        self.assertEqual(b.dtype, paddle.bfloat16)
+        self.assertEqual(b[0], 2.0)
+
+    def test_list_to_tensor_float16(self):
+        a = [paddle.to_tensor(2, dtype=paddle.float16)]
+        b = paddle.to_tensor(a)
+        self.assertEqual(b.dtype, paddle.float16)
+        self.assertEqual(b[0], 2.0)
+
+    def test_list_to_tensor_bfloat16_float32(self):
+        a = [
+            paddle.to_tensor(2, dtype=paddle.bfloat16),
+            paddle.to_tensor(2, dtype=paddle.float32),
+        ]
+        b = paddle.to_tensor(a)
+        self.assertEqual(b.dtype, paddle.float32)
+        self.assertEqual(b[0], 2.0)
+        self.assertEqual(b[1], 2.0)
+
+    def test_list_to_tensor_float16_float32(self):
+        a = [
+            paddle.to_tensor(2, dtype=paddle.float16),
+            paddle.to_tensor(2, dtype=paddle.float32),
+        ]
+        b = paddle.to_tensor(a)
+        self.assertEqual(b.dtype, paddle.float32)
+        self.assertEqual(b[0], 2.0)
+        self.assertEqual(b[1], 2.0)
+
+
 if __name__ == "__main__":
     unittest.main()