1 files changed, 68 insertions, 0 deletions
diff --git a/tensorflow/python/autograph/utils/tensor_list.py b/tensorflow/python/autograph/utils/tensor_list.py
new file mode 100644
index 0000000000..2556f41289
--- /dev/null
+++ b/tensorflow/python/autograph/utils/tensor_list.py
@@ -0,0 +1,68 @@
+# Copyright 2016 The TensorFlow 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.
+# ==============================================================================
+"""A typed list in Python."""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from tensorflow.python.framework import ops
+from tensorflow.python.ops import list_ops
+from tensorflow.python.ops import tensor_array_ops
+
+
+def dynamic_list_append(target, element):
+  """Converts a list append call inline."""
+  if isinstance(target, tensor_array_ops.TensorArray):
+    return target.write(target.size(), element)
+  # TODO(mdan): What's the right way to check this?
+  # TODO(mdan): We may not need this branch.
+  # It may be possible to use TensorList alone if the loop body will not
+  # require wrapping it, although we'd have to think about an autoboxing
+  # mechanism for lists received as parameter.
+  if isinstance(target, ops.Tensor):
+    return list_ops.tensor_list_push_back(target, element)
+
+  # Python targets (including TensorList): fallback to their original append.
+  target.append(element)
+  return target
+
+
+class TensorList(object):
+  """Tensor list wrapper API-compatible with Python built-in list."""
+
+  def __init__(self, shape, dtype):
+    self.dtype = dtype
+    self.shape = shape
+    self.clear()
+
+  def append(self, value):
+    self.list_ = list_ops.tensor_list_push_back(self.list_, value)
+
+  def pop(self):
+    self.list_, value = list_ops.tensor_list_pop_back(self.list_, self.dtype)
+    return value
+
+  def clear(self):
+    self.list_ = list_ops.empty_tensor_list(self.shape, self.dtype)
+
+  def count(self):
+    return list_ops.tensor_list_length(self.list_)
+
+  def __getitem__(self, key):
+    return list_ops.tensor_list_get_item(self.list_, key, self.dtype)
+
+  def __setitem__(self, key, value):
+    self.list_ = list_ops.tensor_list_set_item(self.list_, key, value)