polars.Expr.null_count

Expr.null_count() → Self

Count null values.

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [None, 1, None],
...         "b": [1, 2, 3],
...     }
... )
>>> df.select(pl.all().null_count())
shape: (1, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ u32 ┆ u32 │
╞═════╪═════╡
│ 2   ┆ 0   │
└─────┴─────┘