polars.Expr.arg_sort#

Expr.arg_sort(*, descending: bool = False, nulls_last: bool = False) → Self[source]#

Get the index values that would sort this column.

Parameters:

descending: Sort in descending (descending) order.
nulls_last: Place null values last instead of first.

Returns:

Expr: Expression of data type UInt32.

See also

Expr.gather: Take values by index.
Expr.rank: Get the rank of each row.

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [20, 10, 30],
...         "b": [1, 2, 3],
...     }
... )
>>> df.select(pl.col("a").arg_sort())
shape: (3, 1)
┌─────┐
│ a   │
│ --- │
│ u32 │
╞═════╡
│ 1   │
│ 0   │
│ 2   │
└─────┘

Use gather to apply the arg sort to other columns.

>>> df.select(pl.col("b").gather(pl.col("a").arg_sort()))
shape: (3, 1)
┌─────┐
│ b   │
│ --- │
│ i64 │
╞═════╡
│ 2   │
│ 1   │
│ 3   │
└─────┘