polars.Series.dt.round#

Series.dt.round(
every: str | dt.timedelta,
offset: str | dt.timedelta | None = None,
*,
ambiguous: Ambiguous | Series | None = None,
) → Series[source]#

Divide the date/ datetime range into buckets.

Each date/datetime in the first half of the interval is mapped to the start of its bucket. Each date/datetime in the second half of the interval is mapped to the end of its bucket. Ambiguous results are localised using the DST offset of the original timestamp - for example, rounding '2022-11-06 01:20:00 CST' by '1h' results in '2022-11-06 01:00:00 CST', whereas rounding '2022-11-06 01:20:00 CDT' by '1h' results in '2022-11-06 01:00:00 CDT'.

The every and offset argument are created with the the following string language:

  • 1ns (1 nanosecond)

  • 1us (1 microsecond)

  • 1ms (1 millisecond)

  • 1s (1 second)

  • 1m (1 minute)

  • 1h (1 hour)

  • 1d (1 calendar day)

  • 1w (1 calendar week)

  • 1mo (1 calendar month)

  • 1q (1 calendar quarter)

  • 1y (1 calendar year)

These strings can be combined:

  • 3d12h4m25s # 3 days, 12 hours, 4 minutes, and 25 seconds

By “calendar day”, we mean the corresponding time on the next day (which may not be 24 hours, due to daylight savings). Similarly for “calendar week”, “calendar month”, “calendar quarter”, and “calendar year”.

Parameters:
every

Every interval start and period length

offset

Offset the window

ambiguous

Determine how to deal with ambiguous datetimes:

  • 'raise' (default): raise

  • 'earliest': use the earliest datetime

  • 'latest': use the latest datetime

Deprecated since version 0.19.3: This is now auto-inferred, you can safely remove this argument.

Returns:
Series

Series of data type Date or Datetime.

Warning

This functionality is currently experimental and may change without it being considered a breaking change.

Examples

>>> from datetime import timedelta, datetime
>>> start = datetime(2001, 1, 1)
>>> stop = datetime(2001, 1, 2)
>>> s = pl.datetime_range(start, stop, timedelta(minutes=165), eager=True)
>>> s
shape: (9,)
Series: 'datetime' [datetime[μs]]
[
    2001-01-01 00:00:00
    2001-01-01 02:45:00
    2001-01-01 05:30:00
    2001-01-01 08:15:00
    2001-01-01 11:00:00
    2001-01-01 13:45:00
    2001-01-01 16:30:00
    2001-01-01 19:15:00
    2001-01-01 22:00:00
]
>>> s.dt.round("1h")
shape: (9,)
Series: 'datetime' [datetime[μs]]
[
    2001-01-01 00:00:00
    2001-01-01 03:00:00
    2001-01-01 06:00:00
    2001-01-01 08:00:00
    2001-01-01 11:00:00
    2001-01-01 14:00:00
    2001-01-01 17:00:00
    2001-01-01 19:00:00
    2001-01-01 22:00:00
]
>>> round_str = s.dt.round("1h")
>>> round_td = s.dt.round(timedelta(hours=1))
>>> round_str.equals(round_td)
True

>>> start = datetime(2001, 1, 1)
>>> stop = datetime(2001, 1, 1, 1)
>>> s = pl.datetime_range(start, stop, "10m", eager=True)
>>> s.dt.round("30m")
shape: (7,)
Series: 'datetime' [datetime[μs]]
[
        2001-01-01 00:00:00
        2001-01-01 00:00:00
        2001-01-01 00:30:00
        2001-01-01 00:30:00
        2001-01-01 00:30:00
        2001-01-01 01:00:00
        2001-01-01 01:00:00
]