polars.Expr.backward_fill#
- Expr.backward_fill(limit: int | None = None) Expr [source]#
Fill missing values with the next to be seen values.
- Parameters:
- limit
The number of consecutive null values to backward fill.
See also
Examples
>>> df = pl.DataFrame( ... { ... "a": [1, 2, None], ... "b": [4, None, 6], ... "c": [None, None, 2], ... } ... ) >>> df.select(pl.all().backward_fill()) shape: (3, 3) ┌──────┬─────┬─────┐ │ a ┆ b ┆ c │ │ --- ┆ --- ┆ --- │ │ i64 ┆ i64 ┆ i64 │ ╞══════╪═════╪═════╡ │ 1 ┆ 4 ┆ 2 │ │ 2 ┆ 6 ┆ 2 │ │ null ┆ 6 ┆ 2 │ └──────┴─────┴─────┘ >>> df.select(pl.all().backward_fill(limit=1)) shape: (3, 3) ┌──────┬─────┬──────┐ │ a ┆ b ┆ c │ │ --- ┆ --- ┆ --- │ │ i64 ┆ i64 ┆ i64 │ ╞══════╪═════╪══════╡ │ 1 ┆ 4 ┆ null │ │ 2 ┆ 6 ┆ 2 │ │ null ┆ 6 ┆ 2 │ └──────┴─────┴──────┘