tf.lookup.StaticVocabularyTable

View source on GitHub

Class StaticVocabularyTable

String to Id table wrapper that assigns out-of-vocabulary keys to buckets.

Inherits From: StaticVocabularyTable

Aliases:

For example, if an instance of StaticVocabularyTable is initialized with a string-to-id initializer that maps:

  • emerson -> 0
  • lake -> 1
  • palmer -> 2

The Vocabulary object will performs the following mapping:

  • emerson -> 0
  • lake -> 1
  • palmer -> 2
  • <other term> -> bucket_id, where bucket_id will be between 3 and 3 + num_oov_buckets - 1, calculated by: hash(<term>) % num_oov_buckets + vocab_size

If input_tensor is ["emerson", "lake", "palmer", "king", "crimson"], the lookup result is [0, 1, 2, 4, 7].

If initializer is None, only out-of-vocabulary buckets are used.

Example usage:

num_oov_buckets = 3
input_tensor = tf.constant(["emerson", "lake", "palmer", "king", "crimnson"])
table = tf.lookup.StaticVocabularyTable(
    tf.TextFileIdTableInitializer(filename), num_oov_buckets)
out = table.lookup(input_tensor).
table.init.run()
print(out.eval())

The hash function used for generating out-of-vocabulary buckets ID is Fingerprint64.

__init__

View source

__init__(
    initializer,
    num_oov_buckets,
    lookup_key_dtype=None,
    name=None
)

Construct a StaticVocabularyTable object.

Args:

  • initializer: A TableInitializerBase object that contains the data used to initialize the table. If None, then we only use out-of-vocab buckets.
  • num_oov_buckets: Number of buckets to use for out-of-vocabulary keys. Must be greater than zero.
  • lookup_key_dtype: Data type of keys passed to lookup. Defaults to initializer.key_dtype if initializer is specified, otherwise tf.string. Must be string or integer, and must be castable to initializer.key_dtype.
  • name: A name for the operation (optional).

Raises:

  • ValueError: when num_oov_buckets is not positive.
  • TypeError: when lookup_key_dtype or initializer.key_dtype are not integer or string. Also when initializer.value_dtype != int64.

Properties

initializer

key_dtype

The table key dtype.

name

The name of the table.

resource_handle

Returns the resource handle associated with this Resource.

value_dtype

The table value dtype.

Methods

tf.lookup.StaticVocabularyTable.lookup

View source

lookup(
    keys,
    name=None
)

Looks up keys in the table, outputs the corresponding values.

It assigns out-of-vocabulary keys to buckets based in their hashes.

Args:

  • keys: Keys to look up. May be either a SparseTensor or dense Tensor.
  • name: Optional name for the op.

Returns:

A SparseTensor if keys are sparse, otherwise a dense Tensor.

Raises:

  • TypeError: when keys doesn't match the table key data type.

tf.lookup.StaticVocabularyTable.size

View source

size(name=None)

Compute the number of elements in this table.