[API] added 'place' dummy interface for variable (#45877)

* place

* add test

* fix spell and test

* fix anno

* code style

python/paddle/fluid/layers/math_op_patch.py

@@ -147,6 +147,18 @@ def monkey_patch_variable():
         """
         return self
 
+    @static_only
+    def place(self):
+        """
+        Variable don't have 'place' interface in static mode
+        But this interface can greatly facilitate dy2static.
+        So we give a warnning here and return None.
+        """
+        warnings.warn(
+            "Variable do not have 'place' interface for static mode, try not to use it. None will be returned."
+        )
+        return None
+
     def astype(self, dtype):
         """
         **Notes**:
@@ -427,6 +439,7 @@ def monkey_patch_variable():
         ('astype', astype),
         ('cpu', cpu),
         ('cuda', cuda),
+        ('place', place),
         ('append', append),
         ('item', _item),
         ('pop', pop),

python/paddle/fluid/tests/unittests/dygraph_to_static/test_place.py

+#   Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import numpy as np
+import paddle
+import unittest
+
+
+class TestPlace(unittest.TestCase):
+
+    def test_place(self):
+
+        paddle.enable_static()
+        x = paddle.to_tensor([1, 2, 3, 4])
+        self.assertTrue(x.place() == None)
+
+
+if __name__ == '__main__':
+    unittest.main()