pandas.api.extensions.ExtensionArray.factorize#

ExtensionArray.factorize(use_na_sentinel=True)[source]#

Encode the extension array as an enumerated type.

Parameters:

use_na_sentinelbool, default True: If True, the sentinel -1 will be used for NaN values. If False, NaN values will be encoded as non-negative integers and will not drop the NaN from the uniques of the values.

New in version 1.5.0.

Returns:

codesndarray: An integer NumPy array that’s an indexer into the original ExtensionArray.
uniquesExtensionArray: An ExtensionArray containing the unique values of self.

Note

uniques will not contain an entry for the NA value of the ExtensionArray if there are any missing values present in self.

See also

factorize: Top-level factorize method that dispatches here.

Notes

pandas.factorize() offers a sort keyword as well.

Examples

>>> idx1 = pd.PeriodIndex(["2014-01", "2014-01", "2014-02", "2014-02",
...                       "2014-03", "2014-03"], freq="M")
>>> arr, idx = idx1.factorize()
>>> arr
array([0, 0, 1, 1, 2, 2])
>>> idx
PeriodIndex(['2014-01', '2014-02', '2014-03'], dtype='period[M]')