polars.Expr.bottom_k#

Expr.bottom_k(k: int | IntoExprColumn = 5) Expr[source]#

Return the k smallest elements.

Non-null elements are always preferred over null elements. The output is not guaranteed to be in any particular order, call sort() after this function if you wish the output to be sorted.

This has time complexity:

\[O(n)\]
Parameters:
k

Number of elements to return.

Examples

>>> df = pl.DataFrame(
...     {
...         "value": [1, 98, 2, 3, 99, 4],
...     }
... )
>>> df.select(
...     pl.col("value").top_k().alias("top_k"),
...     pl.col("value").bottom_k().alias("bottom_k"),
... )
shape: (5, 2)
┌───────┬──────────┐
│ top_k ┆ bottom_k │
│ ---   ┆ ---      │
│ i64   ┆ i64      │
╞═══════╪══════════╡
│ 4     ┆ 1        │
│ 98    ┆ 98       │
│ 2     ┆ 2        │
│ 3     ┆ 3        │
│ 99    ┆ 4        │
└───────┴──────────┘