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 Int8.

See also

weekday
ordinal_day

Examples

>>> from datetime import date
>>> df = pl.DataFrame(
...     {
...         "date": pl.date_range(
...             date(2001, 12, 22), date(2001, 12, 25), eager=True
...         )
...     }
... )
>>> 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 │
│ ---        ┆ ---     ┆ ---          ┆ ---         │
│ date       ┆ i8      ┆ i8           ┆ i16         │
╞════════════╪═════════╪══════════════╪═════════════╡
│ 2001-12-22 ┆ 6       ┆ 22           ┆ 356         │
│ 2001-12-23 ┆ 7       ┆ 23           ┆ 357         │
│ 2001-12-24 ┆ 1       ┆ 24           ┆ 358         │
│ 2001-12-25 ┆ 2       ┆ 25           ┆ 359         │
└────────────┴─────────┴──────────────┴─────────────┘