polars.LazyFrame.fill_null#

LazyFrame.fill_null( value: Any | None = None, strategy: FillNullStrategy | None = None, limit: int | None = None, *, matches_supertype: bool = True, ) → Self[source]#

Fill null values using the specified value or strategy.

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.

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 │
└─────┴──────┘