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# Copyright 2018 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.
# ==============================================================================
"""Operators specific to slicing operations."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import collections
from tensorflow.python.framework import dtypes
from tensorflow.python.framework import tensor_util
from tensorflow.python.ops import gen_string_ops
from tensorflow.python.ops import list_ops
from tensorflow.python.ops import tensor_array_ops
# TODO(mdan): Support extended slices.
class GetItemOpts(collections.namedtuple('GetItemOpts', ('element_dtype',))):
pass
def get_item(target, i, opts):
"""The slice read operator (i.e. __getitem__).
Note: it is unspecified whether target will be mutated or not. In general,
if target is mutable (like Python lists), it will be mutated.
Args:
target: An entity that supports getitem semantics.
i: Index to read from.
opts: A GetItemOpts object.
Returns:
The read element.
Raises:
ValueError: if target is not of a supported type.
"""
assert isinstance(opts, GetItemOpts)
if isinstance(target, tensor_array_ops.TensorArray):
return _tf_tensorarray_get_item(target, i)
elif tensor_util.is_tensor(target):
if target.dtype == dtypes.variant:
return _tf_tensor_list_get_item(target, i, opts)
elif target.dtype == dtypes.string and target.shape.ndims == 0:
return _tf_tensor_string_get_item(target, i)
else:
return _tf_tensor_get_item(target, i)
else:
return _py_get_item(target, i)
def _tf_tensorarray_get_item(target, i):
"""Overload of get_item that stages a TensorArray read."""
return target.read(i)
def _tf_tensor_list_get_item(target, i, opts):
"""Overload of get_item that stages a Tensor list read."""
if opts.element_dtype is None:
raise ValueError('cannot retrieve from a list without knowing its '
'element type; use set_element_type to annotate it')
x = list_ops.tensor_list_get_item(target, i, element_dtype=opts.element_dtype)
return x
def _tf_tensor_get_item(target, i):
"""Overload of get_item that stages a Tensor (not Tensor list) read."""
return target[i]
def _tf_tensor_string_get_item(target, i):
"""Overload of get_item that stages a Tensor string read."""
x = gen_string_ops.substr(target, i, 1)
return x
def _py_get_item(target, i):
"""Overload of get_item that executes a Python list modification."""
return target[i]
def set_item(target, i, x):
"""The slice write operator (i.e. __setitem__).
Note: it is unspecified whether target will be mutated or not. In general,
if target is mutable (like Python lists), it will be mutated.
Args:
target: An entity that supports setitem semantics.
i: Index to modify.
x: The new element value.
Returns:
Same as target, after the update was performed.
Raises:
ValueError: if target is not of a supported type.
"""
if isinstance(target, tensor_array_ops.TensorArray):
return _tf_tensorarray_set_item(target, i, x)
elif tensor_util.is_tensor(target):
if target.dtype == dtypes.variant:
return _tf_tensor_list_set_item(target, i, x)
else:
raise ValueError(
'tensor lists are expected to be Tensors with dtype=tf.variant,'
' instead found %s' % target)
else:
return _py_set_item(target, i, x)
def _tf_tensorarray_set_item(target, i, x):
"""Overload of set_item that stages a TensorArray write."""
return target.write(i, x)
def _tf_tensor_list_set_item(target, i, x):
"""Overload of set_item that stages a Tensor list update."""
return list_ops.tensor_list_set_item(target, i, x)
def _py_set_item(target, i, x):
"""Overload of set_item that executes a Python list modification."""
target[i] = x
return target
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