tf.contrib.lookup.string_to_index_table_from_tensor(mapping, num_oov_buckets=0, 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 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]
.
The underlying table must be initialized by calling tf.tables_initializer.run()
or table.init.run()
once.
Elements in mapping
cannot have duplicates, otherwise when executing the table initializer op, it will throw a FailedPreconditionError
.
Sample Usages:
mapping_strings = t.constant(["emerson", "lake", "palmer") table = tf.contrib.lookup.string_to_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.tables_initializer().run() ids.eval() ==> [0, 1, 4, 2]
mapping
: A 1-D string Tensor
that specifies the mapping of strings to indices.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 assignation of out-of-vocabulary buckets.name
: A name for this op (optional).The lookup table to map a string Tensor
to index int64
Tensor
.
ValueError
: mapping
is invalid.ValueError
: If num_oov_buckets
is negative.Defined in tensorflow/contrib/lookup/lookup_ops.py
.
© 2017 The TensorFlow Authors. All rights reserved.
Licensed under the Creative Commons Attribution License 3.0.
Code samples licensed under the Apache 2.0 License.
https://www.tensorflow.org/api_docs/python/tf/contrib/lookup/string_to_index_table_from_tensor