def __init__(self, source, name=None, index=None):
"""A selection from 'source' by a string or numeric 'name_or_index'.
Exactly one of 'name' or 'index' must be specified (not None).
Args:
source: The source value to select from (an instance of
ComputationBuildingBlock).
name: A string name of the element to be selected.
index: A numeric index of the element to be selected.
Raises:
TypeError: if arguments are of the wrong types.
ValueError: if the name is empty or index is negative, or the name/index
is not compatible with the type signature of the source, or neither or
both are defined (not None).
"""
if name is None and index is None:
raise ValueError(
'Must define either a name or index, and neither was specified.'
)
if name is not None and index is not None:
raise ValueError(
'Cannot simultaneously specify a name and an index, choose one.'
)
py_typecheck.check_type(source, ComputationBuildingBlock)
self._source = source
source_type = self._source.type_signature
if not isinstance(source_type, computation_types.NamedTupleType):
raise TypeError(
'Expected the source of selection to be a TFF named tuple, '
'instead found it to be of type {}.'.format(str(source_type)))
if name is not None:
py_typecheck.check_type(name, six.string_types)
if not name:
raise ValueError(
'The name of the selected element cannot be empty.')
else:
# Normalize, in case we are dealing with a Unicode type or some such.
name = str(name)
super(Selection, self).__init__(
type_utils.get_named_tuple_element_type(source_type, name))
self._name = name
self._index = None
else:
# Index must have been specified, since name is None.
py_typecheck.check_type(index, int)
elements = anonymous_tuple.to_elements(source_type)
if index >= 0 and index < len(elements):
super(Selection, self).__init__(elements[index][1])
self._name = None
self._index = index
else:
raise ValueError(
'The index of the selected element {} does not fit into the '
'valid range 0..{} determined by the source type '
'signature.'.format(index, str(len(elements) - 1)))
def test_get_named_tuple_element_type(self):
type_spec = [('a', tf.int32), ('b', tf.bool)]
self.assertEqual(
str(type_utils.get_named_tuple_element_type(type_spec, 'a')), 'int32')
self.assertEqual(
str(type_utils.get_named_tuple_element_type(type_spec, 'b')), 'bool')
with self.assertRaises(ValueError):
type_utils.get_named_tuple_element_type(type_spec, 'c')
with self.assertRaises(TypeError):
type_utils.get_named_tuple_element_type(tf.int32, 'a')
with self.assertRaises(TypeError):
type_utils.get_named_tuple_element_type(type_spec, 10)