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# pandas.api.extensions.ExtensionArray._values_for_factorize

ExtensionArray._values_for_factorize()

  Return an array and missing value suitable for factorization.

  Returns:
    values ndarray

      An array suitable for factorization. This should maintain order and be a supported dtype (Float64, Int64, UInt64, String, Object). By default, the extension array is cast to object dtype.

    na_value object

      The value in values to consider missing. This will be treated as NA in the factorization routines, so it will be coded as -1 and not included in uniques. By default, `np.nan` is used.

  See also

  `util.hash_pandas_object`

    Hash the pandas object.

  Notes

  The values returned by this method are also used in `pandas.util.hash_pandas_object()`. If needed, this can be overridden in the `self._hash_pandas_object()` method.

  Examples

      >>> pd.array([1, 2, 3])._values_for_factorize()
      (array([1, 2, 3], dtype=object), nan)