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# pandas.DatetimeIndex.to_period

DatetimeIndex.to_period(freq=None)

  Cast to PeriodArray/PeriodIndex at a particular frequency.

  Converts DatetimeArray/Index to PeriodArray/PeriodIndex.

  Parameters:
    freq str or Period, optional

      One of pandas’ period aliases or a Period object. Will be inferred by default.

  Returns:
    PeriodArray/PeriodIndex

      Immutable ndarray holding ordinal values at a particular frequency.

  Raises:
    ValueError

      When converting a DatetimeArray/Index with non-regular values, so that a frequency cannot be inferred.

  See also

  `PeriodIndex`

    Immutable ndarray holding ordinal values.

  `DatetimeIndex.to_pydatetime`

    Return DatetimeIndex as object.

  Examples

      >>> df = pd.DataFrame(
      ...     {"y": [1, 2, 3]},
      ...     index=pd.to_datetime(
      ...         [
      ...             "2000-03-31 00:00:00",
      ...             "2000-05-31 00:00:00",
      ...             "2000-08-31 00:00:00",
      ...         ]
      ...     ),
      ... )
      >>> df.index.to_period("M")
      PeriodIndex(['2000-03', '2000-05', '2000-08'],
                  dtype='period[M]')

  Infer the daily frequency

      >>> idx = pd.date_range("2017-01-01", periods=2)
      >>> idx.to_period()
      PeriodIndex(['2017-01-01', '2017-01-02'],
                  dtype='period[D]')