polars.Expr.top_k#

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

Return the k largest 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.

See also

top_k_by
bottom_k
bottom_k_by

Examples

Get the 5 largest values in series.

>>> 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        │
└───────┴──────────┘