polars.Expr.arr.n_unique

Expr.arr.n_unique() → Expr

Count the number of unique values in every sub-arrays.

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [[1, 1, 2], [2, 3, 4]],
...     },
...     schema={"a": pl.Array(pl.Int64, 3)},
... )
>>> df.with_columns(n_unique=pl.col("a").arr.n_unique())
shape: (2, 2)
┌───────────────┬──────────┐
│ a             ┆ n_unique │
│ ---           ┆ ---      │
│ array[i64, 3] ┆ u32      │
╞═══════════════╪══════════╡
│ [1, 1, 2]     ┆ 2        │
│ [2, 3, 4]     ┆ 3        │
└───────────────┴──────────┘