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# Copyright 2021 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.
# ==============================================================================
"""Functions that work with structures.
A structure is either:
* one of the recognized Python collections, holding _nested structures_;
* a value of any other type, typically a TensorFlow data type like Tensor,
Variable, or of compatible types such as int, float, ndarray, etc. these are
commonly referred to as _atoms_ of the structure.
A structure of type `T` is a structure whose atomic items are of type `T`.
For example, a structure of `tf.Tensor` only contains `tf.Tensor` as its atoms.
Historically a _nested structure_ was called a _nested sequence_ in TensorFlow.
A nested structure is sometimes called a _nest_ or a _tree_, but the formal
name _nested structure_ is preferred.
Refer to [Nesting Data Structures]
(https://en.wikipedia.org/wiki/Nesting_(computing)#Data_structures).
The following collection types are recognized by `tf.nest` as nested
structures:
* `collections.abc.Sequence` (except `string` and `bytes`).
This includes `list`, `tuple`, and `namedtuple`.
* `collections.abc.Mapping` (with sortable keys).
This includes `dict` and `collections.OrderedDict`.
* `collections.abc.MappingView` (with sortable keys).
* [`attr.s` classes](https://www.attrs.org/).
* Classes (including
[`dataclass`](https://docs.python.org/library/dataclasses.html))
that implement the `__tf_flatten__` and `__tf_unflatten__` methods.
See examples in
[`nest_util.py`](https://github.com/tensorflow/tensorflow/blob/04869b4e63bfc03cb13627b3e1b879fdd0f69e34/tensorflow/python/util/nest_util.py#L97)
Any other values are considered **atoms**. Not all collection types are
considered nested structures. For example, the following types are
considered atoms:
* `set`; `{"a", "b"}` is an atom, while `["a", "b"]` is a nested structure.
* [`dataclass` classes](https://docs.python.org/library/dataclasses.html) that
don't implement the custom flattening/unflattening methods mentioned above.
* `tf.Tensor`.
* `numpy.array`.
`tf.nest.is_nested` checks whether an object is a nested structure or an atom.
For example:
>>> tf.nest.is_nested("1234")
False
>>> tf.nest.is_nested([1, 3, [4, 5]])
True
>>> tf.nest.is_nested(((7, 8), (5, 6)))
True
>>> tf.nest.is_nested([])
True
>>> tf.nest.is_nested({"a": 1, "b": 2})
True
>>> tf.nest.is_nested({"a": 1, "b": 2}.keys())
True
>>> tf.nest.is_nested({"a": 1, "b": 2}.values())
True
>>> tf.nest.is_nested({"a": 1, "b": 2}.items())
True
>>> tf.nest.is_nested(set([1, 2]))
False
>>> ones = tf.ones([2, 3])
>>> tf.nest.is_nested(ones)
False
Note: A proper structure shall form a tree. The user shall ensure there is no
cyclic references within the items in the structure,
i.e., no references in the structure of the input of these functions
should be recursive. The behavior is undefined if there is a cycle.
API docstring: tensorflow.nest
"""
from tensorflow.python.util import _pywrap_nest
from tensorflow.python.util import _pywrap_utils
from tensorflow.python.util import nest_util
from tensorflow.python.util.tf_export import tf_export
STRUCTURES_HAVE_MISMATCHING_LENGTHS = (
nest_util.STRUCTURES_HAVE_MISMATCHING_LENGTHS
)
STRUCTURES_HAVE_MISMATCHING_TYPES = nest_util.STRUCTURES_HAVE_MISMATCHING_TYPES
SHALLOW_TREE_HAS_INVALID_KEYS = nest_util.SHALLOW_TREE_HAS_INVALID_KEYS
INPUT_TREE_SMALLER_THAN_SHALLOW_TREE = (
nest_util.INPUT_TREE_SMALLER_THAN_SHALLOW_TREE
)
IF_SHALLOW_IS_SEQ_INPUT_MUST_BE_SEQ = (
"If shallow structure is a sequence, input must also be a sequence. "
"Input has type: {}."
)
is_namedtuple = nest_util.is_namedtuple
_is_namedtuple = nest_util.is_namedtuple
_is_attrs = _pywrap_utils.IsAttrs
_is_mapping = _pywrap_utils.IsMapping
same_namedtuples = nest_util.same_namedtuples
def _yield_value(iterable):
return nest_util.yield_value(nest_util.Modality.CORE, iterable)
def _yield_sorted_items(iterable):
return nest_util.yield_sorted_items(nest_util.Modality.CORE, iterable)
@tf_export("__internal__.nest.is_mapping", v1=[])
def is_mapping(obj):
"""Returns a true if its input is a collections.Mapping."""
return _is_mapping(obj)
# TODO(b/225045380): Move to a "leaf" library to use in trace_type.
@tf_export("__internal__.nest.is_attrs", v1=[])
def is_attrs(obj):
"""Returns a true if its input is an instance of an attr.s decorated class."""
return _is_attrs(obj)
@tf_export("__internal__.nest.sequence_like", v1=[])
def _sequence_like(instance, args):
"""Converts the sequence `args` to the same type as `instance`.
Args:
instance: an instance of `tuple`, `list`, `namedtuple`, `dict`,
`collections.OrderedDict`, or `composite_tensor.Composite_Tensor`
or `type_spec.TypeSpec`.
args: items to be converted to the `instance` type.
Returns:
`args` with the type of `instance`.
"""
return nest_util.sequence_like(instance, args)
_is_nested_or_composite = _pywrap_utils.IsNestedOrComposite
@tf_export("nest.is_nested")
def is_nested(seq):
"""Returns true if its input is a nested structure.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a nested structure.
Args:
seq: the value to test.
Returns:
True if the input is a nested structure.
"""
return nest_util.is_nested(nest_util.Modality.CORE, seq)
def is_nested_or_composite(seq):
"""Returns true if its input is a nested structure or a composite.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a nested structure.
Args:
seq: the value to test.
Returns:
True if the input is a nested structure or a composite.
"""
return _is_nested_or_composite(seq)
def is_sequence_or_composite(seq):
return _is_nested_or_composite(seq)
@tf_export("nest.flatten")
def flatten(structure, expand_composites=False):
"""Returns a flat list from a given structure.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a structure.
If the structure is an atom, then returns a single-item list: [structure].
This is the inverse of the `nest.pack_sequence_as` method that takes in a
flattened list and re-packs it into the nested structure.
In the case of dict instances, the sequence consists of the values, sorted by
key to ensure deterministic behavior. This is true also for OrderedDict
instances: their sequence order is ignored, the sorting order of keys is used
instead. The same convention is followed in `nest.pack_sequence_as`. This
correctly repacks dicts and OrderedDicts after they have been flattened, and
also allows flattening an OrderedDict and then repacking it back using a
corresponding plain dict, or vice-versa. Dictionaries with non-sortable keys
cannot be flattened.
Users must not modify any collections used in nest while this function is
running.
Examples:
1. Python dict (ordered by key):
>>> dict = { "key3": "value3", "key1": "value1", "key2": "value2" }
>>> tf.nest.flatten(dict)
['value1', 'value2', 'value3']
2. For a nested python tuple:
>>> tuple = ((1.0, 2.0), (3.0, 4.0, 5.0), 6.0)
>>> tf.nest.flatten(tuple)
[1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
3. For a nested dictionary of dictionaries:
>>> dict = { "key3": {"c": (1.0, 2.0), "a": (3.0)},
... "key1": {"m": "val1", "g": "val2"} }
>>> tf.nest.flatten(dict)
['val2', 'val1', 3.0, 1.0, 2.0]
4. Numpy array (will not flatten):
>>> array = np.array([[1, 2], [3, 4]])
>>> tf.nest.flatten(array)
[array([[1, 2],
[3, 4]])]
5. `tf.Tensor` (will not flatten):
>>> tensor = tf.constant([[1., 2., 3.], [4., 5., 6.], [7., 8., 9.]])
>>> tf.nest.flatten(tensor)
[<tf.Tensor: shape=(3, 3), dtype=float32, numpy=
array([[1., 2., 3.],
[4., 5., 6.],
[7., 8., 9.]], dtype=float32)>]
6. `tf.RaggedTensor`: This is a composite tensor thats representation consists
of a flattened list of 'values' and a list of 'row_splits' which indicate how
to chop up the flattened list into different rows. For more details on
`tf.RaggedTensor`, please visit
https://www.tensorflow.org/api_docs/python/tf/RaggedTensor.
with `expand_composites=False`, we just return the RaggedTensor as is.
>>> tensor = tf.ragged.constant([[3, 1, 4, 1], [], [5, 9, 2]])
>>> tf.nest.flatten(tensor, expand_composites=False)
[<tf.RaggedTensor [[3, 1, 4, 1], [], [5, 9, 2]]>]
with `expand_composites=True`, we return the component Tensors that make up
the RaggedTensor representation (the values and row_splits tensors)
>>> tensor = tf.ragged.constant([[3, 1, 4, 1], [], [5, 9, 2]])
>>> tf.nest.flatten(tensor, expand_composites=True)
[<tf.Tensor: shape=(7,), dtype=int32, numpy=array([3, 1, 4, 1, 5, 9, 2],
dtype=int32)>,
<tf.Tensor: shape=(4,), dtype=int64, numpy=array([0, 4, 4, 7])>]
Args:
structure: an atom or a nested structure. Note, numpy arrays are considered
atoms and are not flattened.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Returns:
A Python list, the flattened version of the input.
Raises:
TypeError: The nest is or contains a dict with non-sortable keys.
"""
return nest_util.flatten(
nest_util.Modality.CORE, structure, expand_composites
)
@tf_export("nest.assert_same_structure")
def assert_same_structure(nest1, nest2, check_types=True,
expand_composites=False):
"""Asserts that two structures are nested in the same way.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a structure.
Note the method does not check the types of atoms inside the structures.
Examples:
* These atom vs. atom comparisons will pass:
>>> tf.nest.assert_same_structure(1.5, tf.Variable(1, tf.uint32))
>>> tf.nest.assert_same_structure("abc", np.array([1, 2]))
* These nested structure vs. nested structure comparisons will pass:
>>> structure1 = (((1, 2), 3), 4, (5, 6))
>>> structure2 = ((("foo1", "foo2"), "foo3"), "foo4", ("foo5", "foo6"))
>>> structure3 = [(("a", "b"), "c"), "d", ["e", "f"]]
>>> tf.nest.assert_same_structure(structure1, structure2)
>>> tf.nest.assert_same_structure(structure1, structure3, check_types=False)
>>> import collections
>>> tf.nest.assert_same_structure(
... collections.namedtuple("bar", "a b")(1, 2),
... collections.namedtuple("foo", "a b")(2, 3),
... check_types=False)
>>> tf.nest.assert_same_structure(
... collections.namedtuple("bar", "a b")(1, 2),
... { "a": 1, "b": 2 },
... check_types=False)
>>> tf.nest.assert_same_structure(
... { "a": 1, "b": 2, "c": 3 },
... { "c": 6, "b": 5, "a": 4 })
>>> ragged_tensor1 = tf.RaggedTensor.from_row_splits(
... values=[3, 1, 4, 1, 5, 9, 2, 6],
... row_splits=[0, 4, 4, 7, 8, 8])
>>> ragged_tensor2 = tf.RaggedTensor.from_row_splits(
... values=[3, 1, 4],
... row_splits=[0, 3])
>>> tf.nest.assert_same_structure(
... ragged_tensor1,
... ragged_tensor2,
... expand_composites=True)
* These examples will raise exceptions:
>>> tf.nest.assert_same_structure([0, 1], np.array([0, 1]))
Traceback (most recent call last):
...
ValueError: The two structures don't have the same nested structure
>>> tf.nest.assert_same_structure(
... collections.namedtuple('bar', 'a b')(1, 2),
... collections.namedtuple('foo', 'a b')(2, 3))
Traceback (most recent call last):
...
TypeError: The two structures don't have the same nested structure
Args:
nest1: an atom or a nested structure.
nest2: an atom or a nested structure.
check_types: if `True` (default) types of structures are checked as well,
including the keys of dictionaries. If set to `False`, for example a list
and a tuple of objects will look the same if they have the same size. Note
that namedtuples with identical name and fields are always considered to
have the same shallow structure. Two types will also be considered the
same if they are both list subtypes (which allows "list" and
"_ListWrapper" from trackable dependency tracking to compare equal).
`check_types=True` only checks type of sub-structures. The types of atoms
are not checked.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Raises:
ValueError: If the two structures do not have the same number of atoms or
if the two structures are not nested in the same way.
TypeError: If the two structures differ in the type of sequence in any of
their substructures. Only possible if `check_types` is `True`.
"""
nest_util.assert_same_structure(
nest_util.Modality.CORE, nest1, nest2, check_types, expand_composites
)
def flatten_dict_items(dictionary):
"""Returns a dictionary with flattened keys and values.
This function flattens the keys and values of a dictionary, which can be
arbitrarily nested structures, and returns the flattened version of such
structures:
```python
example_dictionary = {(4, 5, (6, 8)): ("a", "b", ("c", "d"))}
result = {4: "a", 5: "b", 6: "c", 8: "d"}
flatten_dict_items(example_dictionary) == result
```
The input dictionary must satisfy two properties:
1. Its keys and values should have the same exact nested structure.
2. The set of all flattened keys of the dictionary must not contain repeated
keys.
Args:
dictionary: the dictionary to zip
Returns:
The zipped dictionary.
Raises:
TypeError: If the input is not a dictionary.
ValueError: If any key and value do not have the same structure layout, or
if keys are not unique.
"""
return _pywrap_nest.FlattenDictItems(dictionary)
@tf_export("nest.pack_sequence_as")
def pack_sequence_as(structure, flat_sequence, expand_composites=False):
"""Returns a given flattened sequence packed into a given structure.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a structure.
If `structure` is an atom, `flat_sequence` must be a single-item list;
in this case the return value is `flat_sequence[0]`.
If `structure` is or contains a dict instance, the keys will be sorted to
pack the flat sequence in deterministic order. This is true also for
`OrderedDict` instances: their sequence order is ignored, the sorting order of
keys is used instead. The same convention is followed in `flatten`.
This correctly repacks dicts and `OrderedDict`s after they have been
flattened, and also allows flattening an `OrderedDict` and then repacking it
back using a corresponding plain dict, or vice-versa.
Dictionaries with non-sortable keys cannot be flattened.
Examples:
1. Python dict:
>>> structure = { "key3": "", "key1": "", "key2": "" }
>>> flat_sequence = ["value1", "value2", "value3"]
>>> tf.nest.pack_sequence_as(structure, flat_sequence)
{'key3': 'value3', 'key1': 'value1', 'key2': 'value2'}
2. For a nested python tuple:
>>> structure = (('a','b'), ('c','d','e'), 'f')
>>> flat_sequence = [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
>>> tf.nest.pack_sequence_as(structure, flat_sequence)
((1.0, 2.0), (3.0, 4.0, 5.0), 6.0)
3. For a nested dictionary of dictionaries:
>>> structure = { "key3": {"c": ('alpha', 'beta'), "a": ('gamma')},
... "key1": {"e": "val1", "d": "val2"} }
>>> flat_sequence = ['val2', 'val1', 3.0, 1.0, 2.0]
>>> tf.nest.pack_sequence_as(structure, flat_sequence)
{'key3': {'c': (1.0, 2.0), 'a': 3.0}, 'key1': {'e': 'val1', 'd': 'val2'}}
4. Numpy array (considered a scalar):
>>> structure = ['a']
>>> flat_sequence = [np.array([[1, 2], [3, 4]])]
>>> tf.nest.pack_sequence_as(structure, flat_sequence)
[array([[1, 2],
[3, 4]])]
5. tf.Tensor (considered a scalar):
>>> structure = ['a']
>>> flat_sequence = [tf.constant([[1., 2., 3.], [4., 5., 6.]])]
>>> tf.nest.pack_sequence_as(structure, flat_sequence)
[<tf.Tensor: shape=(2, 3), dtype=float32,
numpy= array([[1., 2., 3.], [4., 5., 6.]], dtype=float32)>]
6. `tf.RaggedTensor`: This is a composite tensor thats representation consists
of a flattened list of 'values' and a list of 'row_splits' which indicate how
to chop up the flattened list into different rows. For more details on
`tf.RaggedTensor`, please visit
https://www.tensorflow.org/api_docs/python/tf/RaggedTensor.
With `expand_composites=False`, we treat RaggedTensor as a scalar.
>>> structure = { "foo": tf.ragged.constant([[1, 2], [3]]),
... "bar": tf.constant([[5]]) }
>>> flat_sequence = [ "one", "two" ]
>>> tf.nest.pack_sequence_as(structure, flat_sequence,
... expand_composites=False)
{'foo': 'two', 'bar': 'one'}
With `expand_composites=True`, we expect that the flattened input contains
the tensors making up the ragged tensor i.e. the values and row_splits
tensors.
>>> structure = { "foo": tf.ragged.constant([[1., 2.], [3.]]),
... "bar": tf.constant([[5.]]) }
>>> tensors = tf.nest.flatten(structure, expand_composites=True)
>>> print(tensors)
[<tf.Tensor: shape=(1, 1), dtype=float32, numpy=array([[5.]],
dtype=float32)>,
<tf.Tensor: shape=(3,), dtype=float32, numpy=array([1., 2., 3.],
dtype=float32)>,
<tf.Tensor: shape=(3,), dtype=int64, numpy=array([0, 2, 3])>]
>>> verified_tensors = [tf.debugging.check_numerics(t, 'invalid tensor: ')
... if t.dtype==tf.float32 else t
... for t in tensors]
>>> tf.nest.pack_sequence_as(structure, verified_tensors,
... expand_composites=True)
{'foo': <tf.RaggedTensor [[1.0, 2.0], [3.0]]>,
'bar': <tf.Tensor: shape=(1, 1), dtype=float32, numpy=array([[5.]],
dtype=float32)>}
Args:
structure: Nested structure, whose structure is given by nested lists,
tuples, and dicts. Note: numpy arrays and strings are considered
scalars.
flat_sequence: flat sequence to pack.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Returns:
packed: `flat_sequence` converted to have the same recursive structure as
`structure`.
Raises:
ValueError: If `flat_sequence` and `structure` have different
atom counts.
TypeError: `structure` is or contains a dict with non-sortable keys.
"""
return nest_util.pack_sequence_as(
nest_util.Modality.CORE, structure, flat_sequence, expand_composites
)
@tf_export("nest.map_structure")
def map_structure(func, *structure, **kwargs):
"""Creates a new structure by applying `func` to each atom in `structure`.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a structure.
Applies `func(x[0], x[1], ...)` where x[i] enumerates all atoms in
`structure[i]`. All items in `structure` must have the same arity,
and the return value will contain results with the same structure layout.
Examples:
* A single Python dict:
>>> a = {"hello": 24, "world": 76}
>>> tf.nest.map_structure(lambda p: p * 2, a)
{'hello': 48, 'world': 152}
* Multiple Python dictionaries:
>>> d1 = {"hello": 24, "world": 76}
>>> d2 = {"hello": 36, "world": 14}
>>> tf.nest.map_structure(lambda p1, p2: p1 + p2, d1, d2)
{'hello': 60, 'world': 90}
* A single Python list:
>>> a = [24, 76, "ab"]
>>> tf.nest.map_structure(lambda p: p * 2, a)
[48, 152, 'abab']
* Scalars:
>>> tf.nest.map_structure(lambda x, y: x + y, 3, 4)
7
* Empty structures:
>>> tf.nest.map_structure(lambda x: x + 1, ())
()
* Check the types of iterables:
>>> s1 = (((1, 2), 3), 4, (5, 6))
>>> s1_list = [[[1, 2], 3], 4, [5, 6]]
>>> tf.nest.map_structure(lambda x, y: None, s1, s1_list)
Traceback (most recent call last):
...
TypeError: The two structures don't have the same nested structure
* Type check is set to False:
>>> s1 = (((1, 2), 3), 4, (5, 6))
>>> s1_list = [[[1, 2], 3], 4, [5, 6]]
>>> tf.nest.map_structure(lambda x, y: None, s1, s1_list, check_types=False)
(((None, None), None), None, (None, None))
Args:
func: A callable that accepts as many arguments as there are structures.
*structure: atom or nested structure.
**kwargs: Valid keyword args are:
* `check_types`: If set to `True` (default) the types of iterables within
the structures have to be same (e.g. `map_structure(func, [1], (1,))`
raises a `TypeError` exception). To allow this set this argument to
`False`. Note that namedtuples with identical name and fields are always
considered to have the same shallow structure.
* `expand_composites`: If set to `True`, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors. If `False` (the default), then composite tensors are
not expanded.
Returns:
A new structure with the same arity as `structure[0]`, whose atoms
correspond to `func(x[0], x[1], ...)` where `x[i]` is the atom in the
corresponding location in `structure[i]`. If there are different structure
types and `check_types` is `False` the structure types of the first
structure will be used.
Raises:
TypeError: If `func` is not callable or if the structures do not match
each other by depth tree.
ValueError: If no structure is provided or if the structures do not match
each other by type.
ValueError: If wrong keyword arguments are provided.
"""
return nest_util.map_structure(
nest_util.Modality.CORE, func, *structure, **kwargs
)
def map_structure_with_paths(func, *structure, **kwargs):
"""Applies `func` to each entry in `structure` and returns a new structure.
Applies `func(path, x[0], x[1], ..., **kwargs)` where x[i] is an entry in
`structure[i]` and `path` is the common path to x[i] in the structures. All
structures in `structure` must have the same arity, and the return value will
contain the results with the same structure layout. Special kwarg
`check_types` determines whether the types of iterables within the structure
must be the same-- see **kwargs definition below.
Args:
func: A callable with the signature func(path, *values, **kwargs) that is
evaluated on the leaves of the structure.
*structure: A variable number of compatible structures to process.
**kwargs: Optional kwargs to be passed through to func. Special kwarg
`check_types` is not passed to func, but instead determines whether the
types of iterables within the structures have to be same (e.g.,
`map_structure(func, [1], (1,))` raises a `TypeError` exception). By
default, the types must match. To allow iteration over structures of
different types (but common arity), set this kwarg to `False`.
Returns:
A structure of the same form as the input structures whose leaves are the
result of evaluating func on corresponding leaves of the input structures.
Raises:
TypeError: If `func` is not callable or if the structures do not match
each other by depth tree.
TypeError: If `check_types` is not `False` and the two structures differ in
the type of sequence in any of their substructures.
ValueError: If no structures are provided.
"""
def wrapper_func(tuple_path, *inputs, **kwargs):
string_path = "/".join(str(s) for s in tuple_path)
return func(string_path, *inputs, **kwargs)
return nest_util.map_structure_up_to(
nest_util.Modality.CORE, structure[0], wrapper_func, *structure, **kwargs
)
def map_structure_with_tuple_paths(func, *structure, **kwargs):
"""Applies `func` to each entry in `structure` and returns a new structure.
Applies `func(tuple_path, x[0], x[1], ..., **kwargs)` where `x[i]` is an entry
in `structure[i]` and `tuple_path` is a tuple of indices and/or dictionary
keys (as returned by `nest.yield_flat_paths`), which uniquely specifies the
common path to x[i] in the structures. All structures in `structure` must have
the same arity, and the return value will contain the results in the same
structure. Special kwarg `check_types` determines whether the types of
iterables within the structure must be the same-- see **kwargs definition
below.
Args:
func: A callable with the signature `func(tuple_path, *values, **kwargs)`
that is evaluated on the leaves of the structure.
*structure: A variable number of compatible structures to process.
**kwargs: Optional kwargs to be passed through to func. Special kwarg
`check_types` is not passed to func, but instead determines whether the
types of iterables within the structures have to be same (e.g.
`map_structure(func, [1], (1,))` raises a `TypeError` exception). To allow
this set this argument to `False`.
Returns:
A structure of the same form as the input structures whose leaves are the
result of evaluating func on corresponding leaves of the input structures.
Raises:
TypeError: If `func` is not callable or if the structures do not match
each other by depth tree.
TypeError: If `check_types` is not `False` and the two structures differ in
the type of sequence in any of their substructures.
ValueError: If no structures are provided.
"""
return nest_util.map_structure_up_to(
nest_util.Modality.CORE, structure[0], func, *structure, **kwargs
)
def assert_shallow_structure(shallow_tree,
input_tree,
check_types=True,
expand_composites=False):
"""Asserts that `shallow_tree` is a shallow structure of `input_tree`.
That is, this function tests if the `input_tree` structure can be created from
the `shallow_tree` structure by replacing its leaf nodes with deeper
tree structures.
Examples:
The following code will raise an exception:
```python
shallow_tree = {"a": "A", "b": "B"}
input_tree = {"a": 1, "c": 2}
assert_shallow_structure(shallow_tree, input_tree)
```
The following code will raise an exception:
```python
shallow_tree = ["a", "b"]
input_tree = ["c", ["d", "e"], "f"]
assert_shallow_structure(shallow_tree, input_tree)
```
Args:
shallow_tree: an arbitrarily nested structure.
input_tree: an arbitrarily nested structure.
check_types: if `True` (default) the sequence types of `shallow_tree` and
`input_tree` have to be the same. Note that even with check_types==True,
this function will consider two different namedtuple classes with the same
name and _fields attribute to be the same class.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Raises:
TypeError: If `shallow_tree` is a sequence but `input_tree` is not.
TypeError: If the sequence types of `shallow_tree` are different from
`input_tree`. Only raised if `check_types` is `True`.
ValueError: If the sequence lengths of `shallow_tree` are different from
`input_tree`.
"""
nest_util.assert_shallow_structure(
nest_util.Modality.CORE,
shallow_tree,
input_tree,
check_types,
expand_composites,
)
@tf_export("__internal__.nest.flatten_up_to", v1=[])
def flatten_up_to(shallow_tree, input_tree, check_types=True,
expand_composites=False):
"""Flattens `input_tree` up to `shallow_tree`.
Refer to [tf.nest](https://www.tensorflow.org/api_docs/python/tf/nest)
for the definition of a structure.
Any further depth in structure in `input_tree` is retained as structures in
the partially flatten output.
If `shallow_tree` and `input_tree` are atoms, this returns a
single-item list: `[input_tree]`.
Use Case:
Sometimes we may wish to partially flatten a structure, retaining some
of the nested structure. We achieve this by specifying a shallow structure,
`shallow_tree`, we wish to flatten up to.
The input, `input_tree`, can be thought of as having the same structure layout
as `shallow_tree`, but with leaf nodes that are themselves tree structures.
Examples:
```python
input_tree = [[[2, 2], [3, 3]], [[4, 9], [5, 5]]]
shallow_tree = [[True, True], [False, True]]
flattened_input_tree = flatten_up_to(shallow_tree, input_tree)
flattened_shallow_tree = flatten_up_to(shallow_tree, shallow_tree)
# Output is:
# [[2, 2], [3, 3], [4, 9], [5, 5]]
# [True, True, False, True]
```
```python
input_tree = [[('a', 1), [('b', 2), [('c', 3), [('d', 4)]]]]]
shallow_tree = [['level_1', ['level_2', ['level_3', ['level_4']]]]]
input_tree_flattened_as_shallow_tree = flatten_up_to(shallow_tree, input_tree)
input_tree_flattened = flatten(input_tree)
# Output is:
# [('a', 1), ('b', 2), ('c', 3), ('d', 4)]
# ['a', 1, 'b', 2, 'c', 3, 'd', 4]
```
Edge Cases for atoms:
```python
flatten_up_to(0, 0) # Output: [0]
flatten_up_to(0, [0, 1, 2]) # Output: [[0, 1, 2]]
flatten_up_to([0, 1, 2], 0) # Output: TypeError
flatten_up_to([0, 1, 2], [0, 1, 2]) # Output: [0, 1, 2]
```
Args:
shallow_tree: a possibly pruned structure of input_tree.
input_tree: an atom or a nested structure.
Note, numpy arrays are considered atoms.
check_types: bool. If True, check that each node in shallow_tree has the
same type as the corresponding node in input_tree.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Returns:
A Python list, the partially flattened version of `input_tree` according to
the structure of `shallow_tree`.
Raises:
TypeError: If `shallow_tree` is a nested structure but `input_tree` is not.
TypeError: If the structure types of `shallow_tree` are different from
`input_tree`.
ValueError: If the structure lengths of `shallow_tree` are different from
`input_tree`.
"""
return nest_util.flatten_up_to(
nest_util.Modality.CORE,
shallow_tree,
input_tree,
check_types,
expand_composites,
)
def flatten_with_tuple_paths_up_to(shallow_tree,
input_tree,
check_types=True,
expand_composites=False):
"""Flattens `input_tree` up to `shallow_tree`.
Any further depth in structure in `input_tree` is retained as structures in
the partially flattened output.
Returns a list of (path, value) pairs, where value a leaf node in the
flattened tree, and path is the tuple path of that leaf in input_tree.
If `shallow_tree` and `input_tree` are not sequences, this returns a
single-item list: `[((), input_tree)]`.
Use Case:
Sometimes we may wish to partially flatten a nested sequence, retaining some
of the nested structure. We achieve this by specifying a shallow structure,
`shallow_tree`, we wish to flatten up to.
The input, `input_tree`, can be thought of as having the same structure layout
as `shallow_tree`, but with leaf nodes that are themselves tree structures.
Examples:
```python
input_tree = [[[2, 2], [3, 3]], [[4, 9], [5, 5]]]
shallow_tree = [[True, True], [False, True]]
flattened_input_tree = flatten_with_tuple_paths_up_to(shallow_tree,
input_tree)
flattened_shallow_tree = flatten_with_tuple_paths_up_to(shallow_tree,
shallow_tree)
# Output is:
# [((0, 0), [2, 2]),
# ((0, 1), [3, 3]),
# ((1, 0), [4, 9]),
# ((1, 1), [5, 5])]
#
# [((0, 0), True),
# ((0, 1), True),
# ((1, 0), False),
# ((1, 1), True)]
```
```python
input_tree = [[('a', 1), [('b', 2), [('c', 3), [('d', 4)]]]]]
shallow_tree = [['level_1', ['level_2', ['level_3', ['level_4']]]]]
input_tree_flattened_as_shallow_tree = flatten_up_to(shallow_tree, input_tree)
input_tree_flattened = flatten(input_tree)
# Output is:
# [((0, 0), ('a', 1)),
# ((0, 1, 0), ('b', 2)),
# ((0, 1, 1, 0), ('c', 3)),
# ((0, 1, 1, 1), ('d', 4))]
# ['a', 1, 'b', 2, 'c', 3, 'd', 4]
```
Non-Sequence Edge Cases:
```python
flatten_with_tuple_paths_up_to(0, 0) # Output: [(), 0]
flatten_with_tuple_paths_up_to(0, [0, 1, 2]) # Output: [(), [0, 1, 2]]
flatten_with_tuple_paths_up_to([0, 1, 2], 0) # Output: TypeError
flatten_with_tuple_paths_up_to([0, 1, 2], [0, 1, 2])
# Output: [((0,) 0), ((1,), 1), ((2,), 2)]
```
Args:
shallow_tree: a possibly pruned structure of input_tree.
input_tree: an atom or a nested structure.
Note, numpy arrays are considered atoms.
check_types: bool. If True, check that each node in shallow_tree has the
same type as the corresponding node in input_tree.
expand_composites: If true, then composite tensors such as
`tf.sparse.SparseTensor` and `tf.RaggedTensor` are expanded into their
component tensors.
Returns:
A Python list, the partially flattened version of `input_tree` according to
the structure of `shallow_tree`.
Raises:
TypeError: If `shallow_tree` is a nested structure but `input_tree` is not.
TypeError: If the structure types of `shallow_tree` are different from
`input_tree`.
ValueError: If the structure lengths of `shallow_tree` are different from
`input_tree`.
"""
is_nested_fn = _is_nested_or_composite if expand_composites else is_nested
assert_shallow_structure(shallow_tree,
input_tree,
check_types=check_types,
expand_composites=expand_composites)
return list(
nest_util.yield_flat_up_to(
nest_util.Modality.CORE, shallow_tree, input_tree, is_nested_fn
)
)
@tf_export("__internal__.nest.map_structure_up_to", v1=[])
def map_structure_up_to(shallow_tree, func, *inputs, **kwargs):
"""Applies a function or op to a number of partially flattened inputs.
The `inputs` are flattened up to `shallow_tree` before being mapped.
Use Case:
Sometimes we wish to apply a function to a partially flattened
structure (for example when the function itself takes structure inputs). We
achieve this by specifying a shallow structure, `shallow_tree` we wish to
flatten up to.
The `inputs`, can be thought of as having the same structure layout as
`shallow_tree`, but with leaf nodes that are themselves tree structures.
This function therefore will return something with the same base structure as
`shallow_tree`.
Examples:
```python
shallow_tree = [None, None]
inp_val = [1, 2, 3]
out = map_structure_up_to(shallow_tree, lambda x: 2 * x, inp_val)
# Output is: [2, 4]
```
```python
ab_tuple = collections.namedtuple("ab_tuple", "a, b")
op_tuple = collections.namedtuple("op_tuple", "add, mul")
inp_val = ab_tuple(a=2, b=3)
inp_ops = ab_tuple(a=op_tuple(add=1, mul=2), b=op_tuple(add=2, mul=3))
out = map_structure_up_to(inp_val, lambda val, ops: (val + ops.add) * ops.mul,
inp_val, inp_ops)
# Output is: ab_tuple(a=6, b=15)
```
```python
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