polars.Expr.dt.truncate#

Expr.dt.truncate(every: str | timedelta, offset: str | timedelta | None = None) → Expr[source]#

Divide the date/datetime range into buckets.

Each date/datetime is mapped to the start of its bucket.

Parameters:
every

Every interval start and period length

offset

Offset the window

Returns:
Date/Datetime series

Notes

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 day

  • 1w # 1 calendar week

  • 1mo # 1 calendar month

  • 1y # 1 calendar year

These strings can be combined:

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

Examples

>>> from datetime import timedelta, datetime
>>> start = datetime(2001, 1, 1)
>>> stop = datetime(2001, 1, 2)
>>> df = pl.date_range(
...     start, stop, timedelta(minutes=225), name="dates"
... ).to_frame()
>>> df
shape: (7, 1)
┌─────────────────────┐
│ dates               │
│ ---                 │
│ datetime[μs]        │
╞═════════════════════╡
│ 2001-01-01 00:00:00 │
│ 2001-01-01 03:45:00 │
│ 2001-01-01 07:30:00 │
│ 2001-01-01 11:15:00 │
│ 2001-01-01 15:00:00 │
│ 2001-01-01 18:45:00 │
│ 2001-01-01 22:30:00 │
└─────────────────────┘
>>> df.select(pl.col("dates").dt.truncate("1h"))
shape: (7, 1)
┌─────────────────────┐
│ dates               │
│ ---                 │
│ datetime[μs]        │
╞═════════════════════╡
│ 2001-01-01 00:00:00 │
│ 2001-01-01 03:00:00 │
│ 2001-01-01 07:00:00 │
│ 2001-01-01 11:00:00 │
│ 2001-01-01 15:00:00 │
│ 2001-01-01 18:00:00 │
│ 2001-01-01 22:00:00 │
└─────────────────────┘
>>> df.select(pl.col("dates").dt.truncate("1h")).frame_equal(
...     df.select(pl.col("dates").dt.truncate(timedelta(hours=1)))
... )
True

>>> start = datetime(2001, 1, 1)
>>> stop = datetime(2001, 1, 1, 1)
>>> df = pl.date_range(start, stop, "10m", name="dates").to_frame()
>>> df.select(["dates", pl.col("dates").dt.truncate("30m").alias("truncate")])
shape: (7, 2)
┌─────────────────────┬─────────────────────┐
│ dates               ┆ truncate            │
│ ---                 ┆ ---                 │
│ datetime[μs]        ┆ datetime[μs]        │
╞═════════════════════╪═════════════════════╡
│ 2001-01-01 00:00:00 ┆ 2001-01-01 00:00:00 │
│ 2001-01-01 00:10:00 ┆ 2001-01-01 00:00:00 │
│ 2001-01-01 00:20:00 ┆ 2001-01-01 00:00:00 │
│ 2001-01-01 00:30:00 ┆ 2001-01-01 00:30:00 │
│ 2001-01-01 00:40:00 ┆ 2001-01-01 00:30:00 │
│ 2001-01-01 00:50:00 ┆ 2001-01-01 00:30:00 │
│ 2001-01-01 01:00:00 ┆ 2001-01-01 01:00:00 │
└─────────────────────┴─────────────────────┘