polars.Expr.dt.iso_year#

Expr.dt.iso_year() → Expr[source]#

Extract ISO year from underlying Date representation.

Applies to Date and Datetime columns.

Returns the year number in the ISO standard. This may not correspond with the calendar year.

Returns:

Expr: Expression of data type Int32.

Examples

>>> from datetime import date
>>> df = pl.DataFrame(
...     {"date": [date(1977, 1, 1), date(1978, 1, 1), date(1979, 1, 1)]}
... )
>>> df.select(
...     "date",
...     pl.col("date").dt.year().alias("calendar_year"),
...     pl.col("date").dt.iso_year().alias("iso_year"),
... )
shape: (3, 3)
┌────────────┬───────────────┬──────────┐
│ date       ┆ calendar_year ┆ iso_year │
│ ---        ┆ ---           ┆ ---      │
│ date       ┆ i32           ┆ i32      │
╞════════════╪═══════════════╪══════════╡
│ 1977-01-01 ┆ 1977          ┆ 1976     │
│ 1978-01-01 ┆ 1978          ┆ 1977     │
│ 1979-01-01 ┆ 1979          ┆ 1979     │
└────────────┴───────────────┴──────────┘