polars.LazyFrame.fill_null

LazyFrame.fill_null(
    value: Any | Expr | None = None,
    strategy: FillNullStrategy | None = None,
    limit: int | None = None,
    *,
    matches_supertype: bool = True,
) → LazyFrame

Fill null values using the specified value or strategy.

engine:In MemoryStreamingPartially Distributed

Parameters:

value

Value used to fill null values.

strategy{None, ‘forward’, ‘backward’, ‘min’, ‘max’, ‘mean’, ‘zero’, ‘one’}

Strategy used to fill null values.

limit

Number of consecutive null values to fill when using the ‘forward’ or ‘backward’ strategy.

matches_supertype

Fill all matching supertypes of the fill value literal.

See also

fill_nan

Notes

A null value is not the same as a NaN value. To fill NaN values, use fill_nan().

Examples

>>> lf = pl.LazyFrame(
...     {
...         "a": [1, 2, None, 4],
...         "b": [0.5, 4, None, 13],
...     }
... )
>>> lf.fill_null(99).collect()
shape: (4, 2)
┌─────┬──────┐
│ a   ┆ b    │
│ --- ┆ ---  │
│ i64 ┆ f64  │
╞═════╪══════╡
│ 1   ┆ 0.5  │
│ 2   ┆ 4.0  │
│ 99  ┆ 99.0 │
│ 4   ┆ 13.0 │
└─────┴──────┘
>>> lf.fill_null(strategy="forward").collect()
shape: (4, 2)
┌─────┬──────┐
│ a   ┆ b    │
│ --- ┆ ---  │
│ i64 ┆ f64  │
╞═════╪══════╡
│ 1   ┆ 0.5  │
│ 2   ┆ 4.0  │
│ 2   ┆ 4.0  │
│ 4   ┆ 13.0 │
└─────┴──────┘

>>> lf.fill_null(strategy="max").collect()
shape: (4, 2)
┌─────┬──────┐
│ a   ┆ b    │
│ --- ┆ ---  │
│ i64 ┆ f64  │
╞═════╪══════╡
│ 1   ┆ 0.5  │
│ 2   ┆ 4.0  │
│ 4   ┆ 13.0 │
│ 4   ┆ 13.0 │
└─────┴──────┘

>>> lf.fill_null(strategy="zero").collect()
shape: (4, 2)
┌─────┬──────┐
│ a   ┆ b    │
│ --- ┆ ---  │
│ i64 ┆ f64  │
╞═════╪══════╡
│ 1   ┆ 0.5  │
│ 2   ┆ 4.0  │
│ 0   ┆ 0.0  │
│ 4   ┆ 13.0 │
└─────┴──────┘