polars.LazyFrame.shift_and_fill#

LazyFrame.shift_and_fill( fill_value: Expr | int | str | float, *, periods: int = 1, ) → Self[source]#

Shift the values by a given period and fill the resulting null values.

Parameters:

fill_value: fill None values with the result of this expression.
periods: Number of places to shift (may be negative).

Examples

>>> lf = pl.LazyFrame(
...     {
...         "a": [1, 3, 5],
...         "b": [2, 4, 6],
...     }
... )
>>> lf.shift_and_fill(fill_value=0, periods=1).collect()
shape: (3, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 0   ┆ 0   │
│ 1   ┆ 2   │
│ 3   ┆ 4   │
└─────┴─────┘
>>> lf.shift_and_fill(periods=-1, fill_value=0).collect()
shape: (3, 2)
┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ i64 │
╞═════╪═════╡
│ 3   ┆ 4   │
│ 5   ┆ 6   │
│ 0   ┆ 0   │
└─────┴─────┘