polars.Expr.dt.day#

Expr.dt.day() → Expr[source]#

Extract day from underlying Date representation.

Applies to Date and Datetime columns.

Returns the day of month starting from 1. The return value ranges from 1 to 31. (The last day of month differs by months.)

Returns:

Expr: Expression of data type UInt32.

See also

weekday
ordinal_day

Examples

>>> from datetime import timedelta, datetime
>>> start = datetime(2001, 12, 22)
>>> stop = datetime(2001, 12, 25)
>>> df = pl.DataFrame(
...     {"date": pl.date_range(start, stop, timedelta(days=1), eager=True)}
... )
>>> df
shape: (4, 1)
┌─────────────────────┐
│ date                │
│ ---                 │
│ datetime[μs]        │
╞═════════════════════╡
│ 2001-12-22 00:00:00 │
│ 2001-12-23 00:00:00 │
│ 2001-12-24 00:00:00 │
│ 2001-12-25 00:00:00 │
└─────────────────────┘
>>> df.with_columns(
...     pl.col("date").dt.weekday().alias("weekday"),
...     pl.col("date").dt.day().alias("day_of_month"),
...     pl.col("date").dt.ordinal_day().alias("day_of_year"),
... )
shape: (4, 4)
┌─────────────────────┬─────────┬──────────────┬─────────────┐
│ date                ┆ weekday ┆ day_of_month ┆ day_of_year │
│ ---                 ┆ ---     ┆ ---          ┆ ---         │
│ datetime[μs]        ┆ u32     ┆ u32          ┆ u32         │
╞═════════════════════╪═════════╪══════════════╪═════════════╡
│ 2001-12-22 00:00:00 ┆ 6       ┆ 22           ┆ 356         │
│ 2001-12-23 00:00:00 ┆ 7       ┆ 23           ┆ 357         │
│ 2001-12-24 00:00:00 ┆ 1       ┆ 24           ┆ 358         │
│ 2001-12-25 00:00:00 ┆ 2       ┆ 25           ┆ 359         │
└─────────────────────┴─────────┴──────────────┴─────────────┘