# tf.contrib.lookup.string_to_index_table_from_file(vocabulary_file=None, num_oov_buckets=0, vocab_size=None, default_value=-1, hasher_spec=tf.contrib.lookup.FastHashSpec, name=None)

### tf.contrib.lookup.string_to_index_table_from_file(vocabulary_file=None, num_oov_buckets=0, vocab_size=None, default_value=-1, hasher_spec=tf.contrib.lookup.FastHashSpec, name=None)

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

This operation constructs a lookup table to convert tensor of strings into int64 IDs. The mapping can be initialized from a vocabulary file specified in vocabulary_file, where the whole line is the key and the zero-based line number is the ID.

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 [vocabulary size, vocabulary size + num_oov_buckets].

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

Sample Usages:

If we have a vocabulary file "test.txt" with the following content:

emerson
lake
palmer

features = tf.constant(["emerson", "lake", "and", "palmer"])
table = tf.contrib.lookup.string_to_index_table_from_file(
vocabulary_file="test.txt", num_oov_buckets=1)
ids = table.lookup(features)
...
tf.tables_initializer().run()

ids.eval()  ==> [0, 1, 3, 2]  # where 3 is the out-of-vocabulary bucket


#### Args:

• vocabulary_file: The vocabulary filename.
• num_oov_buckets: The number of out-of-vocabulary buckets.
• vocab_size: Number of the elements in the vocabulary, if known.
• 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 assignation of out-of-vocabulary buckets.
• name: A name for this op (optional).

#### Returns:

The lookup table to map a string Tensor to index int64 Tensor.

#### Raises:

• ValueError: If vocabulary_file is not set.
• ValueError: If num_oov_buckets is negative or vocab_size is not greater than zero.