polars.Expr.n_unique

Expr.n_unique() → Self

Count unique values.

Notes

null is considered to be a unique value for the purposes of this operation.

Examples

>>> df = pl.DataFrame({"x": [1, 1, 2, 2, 3], "y": [1, 1, 1, None, None]})
>>> df.select(
...     x_unique=pl.col("x").n_unique(),
...     y_unique=pl.col("y").n_unique(),
... )
shape: (1, 2)
┌──────────┬──────────┐
│ x_unique ┆ y_unique │
│ ---      ┆ ---      │
│ u32      ┆ u32      │
╞══════════╪══════════╡
│ 3        ┆ 2        │
└──────────┴──────────┘