ExtensionArray._values_for_factorize(self) → Tuple[numpy.ndarray, Any][source]

Return an array and missing value suitable for factorization.

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 na_sentinal and not included in uniques. By default, np.nan is used.


The values returned by this method are also used in pandas.util.hash_pandas_object().

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