Series.to_period(freq=None, copy=None)[source]#

Convert Series from DatetimeIndex to PeriodIndex.

freqstr, default None

Frequency associated with the PeriodIndex.

copybool, default True

Whether or not to return a copy.


The copy keyword will change behavior in pandas 3.0. Copy-on-Write will be enabled by default, which means that all methods with a copy keyword will use a lazy copy mechanism to defer the copy and ignore the copy keyword. The copy keyword will be removed in a future version of pandas.

You can already get the future behavior and improvements through enabling copy on write pd.options.mode.copy_on_write = True


Series with index converted to PeriodIndex.


>>> idx = pd.DatetimeIndex(["2023", "2024", "2025"])
>>> s = pd.Series([1, 2, 3], index=idx)
>>> s = s.to_period()
>>> s
2023    1
2024    2
2025    3
Freq: Y-DEC, dtype: int64

Viewing the index

>>> s.index
PeriodIndex(['2023', '2024', '2025'], dtype='period[Y-DEC]')