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Generates a vocabulary for x and maps it to an integer with this vocab.

In case one of the tokens contains the '\n' or '\r' characters or is empty it will be discarded since we are currently writing the vocabularies as text files. This behavior will likely be fixed/improved in the future.

Note that this function will cause a vocabulary to be computed. For large datasets it is highly recommended to either set frequency_threshold or top_k to control the size of the vocabulary, and also the run time of this operation.


  • x: A Tensor or SparseTensor of type tf.string.
  • default_value: The value to use for out-of-vocabulary values, unless 'num_oov_buckets' is greater than zero.
  • top_k: Limit the generated vocabulary to the first top_k elements. If set to None, the full vocabulary is generated.
  • frequency_threshold: Limit the generated vocabulary only to elements whose absolute frequency is >= to the supplied threshold. If set to None, the full vocabulary is generated. Absolute frequency means the number of occurences of the element in the dataset, as opposed to the proportion of instances that contain that element.
  • num_oov_buckets: 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.
  • vocab_filename: The file name for the vocabulary file. If None, a name based on the scope name in the context of this graph will be used as the file name. If not None, should be unique within a given preprocessing function. NOTE in order to make your pipelines resilient to implementation details please set vocab_filename when you are using the vocab_filename on a downstream component.
  • weights: (Optional) Weights Tensor for the vocabulary. It must have the same shape as x.
  • labels: (Optional) Labels Tensor for the vocabulary. It must have dtype int64, have values 0 or 1, and have the same shape as x.
  • use_adjusted_mutual_info: If true, use adjusted mutual information.
  • min_diff_from_avg: Mutual information of a feature will be adjusted to zero whenever the difference between count of the feature with any label and its expected count is lower than min_diff_from_average.
  • coverage_top_k: (Optional), (Experimental) The minimum number of elements per key to be included in the vocabulary.
  • coverage_frequency_threshold: (Optional), (Experimental) Limit the coverage arm of the vocabulary only to elements whose absolute frequency is >= this threshold for a given key.
  • key_fn: (Optional), (Experimental) A fn that takes in a single entry of x and returns the corresponding key for coverage calculation. If this is None, no coverage arm is added to the vocabulary.
  • name: (Optional) A name for this operation.


A Tensor or SparseTensor where each string value is mapped to an integer. Each unique string value that appears in the vocabulary is mapped to a different integer and integers are consecutive starting from zero. String value not in the vocabulary is assigned default_value.


  • ValueError: If top_k or frequency_threshold is negative. If coverage_top_k or coverage_frequency_threshold is negative.