tf.contrib.lookup.index_table_from_tensor

Returns a lookup table that converts a string tensor into int64 IDs.

tf.contrib.lookup.index_table_from_tensor(
    mapping, num_oov_buckets=0, default_value=-1,
    hasher_spec=tf.contrib.lookup.FastHashSpec, dtype=tf.dtypes.string, name=None
)

This operation constructs a lookup table to convert tensor of strings into int64 IDs. The mapping can be initialized from a string mapping 1-D tensor where each element is a key and corresponding index within the tensor is the value.

Any lookup of an out-of-vocabulary token will return a bucket ID based on its hash if num_oov_buckets is greater than zero. Otherwise it is assigned the default_value. The bucket ID range is [mapping size, mapping size + num_oov_buckets - 1].

The underlying table must be initialized by calling session.run(tf.compat.v1.tables_initializer) or session.run(table.init) once.

Elements in mapping cannot have duplicates, otherwise when executing the table initializer op, it will throw a FailedPreconditionError.

Sample Usages:

mapping_strings = tf.constant(["emerson", "lake", "palmer"])
table = tf.contrib.lookup.index_table_from_tensor(
    mapping=mapping_strings, num_oov_buckets=1, default_value=-1)
features = tf.constant(["emerson", "lake", "and", "palmer"])
ids = table.lookup(features)
...
tf.compat.v1.tables_initializer().run()

ids.eval()  ==> [0, 1, 3, 2]

Args
mapping	A 1-D Tensor that specifies the mapping of keys to indices. The type of this object must be castable to dtype.
num_oov_buckets	The number of out-of-vocabulary buckets.
default_value	The value to use for out-of-vocabulary feature values. Defaults to -1.
hasher_spec	A HasherSpec to specify the hash function to use for assignment of out-of-vocabulary buckets.
dtype	The type of values passed to lookup. Only string and integers are supported.
name	A name for this op (optional).

Returns
The lookup table to map an input Tensor to index int64 Tensor.

Raises
ValueError	If mapping is invalid.
ValueError	If num_oov_buckets is negative.