polars.DataFrame.unstack#

DataFrame.unstack(step: int, how: UnstackDirection = 'vertical', columns: str | Sequence[str] | None = None, fill_values: list[Any] | None = None) → Self[source]#

Unstack a long table to a wide form without doing an aggregation.

This can be much faster than a pivot, because it can skip the grouping phase.

Parameters:

step: Number of rows in the unstacked frame.
how{ ‘vertical’, ‘horizontal’ }: Direction of the unstack.
columns: Name of the column(s) to include in the operation. If set to None (default), use all columns.
fill_values: Fill values that don’t fit the new size with this value.

Warning

This functionality is experimental and may be subject to changes without it being considered a breaking change.

Examples

>>> from string import ascii_uppercase
>>> df = pl.DataFrame(
...     {
...         "col1": list(ascii_uppercase[0:9]),
...         "col2": pl.arange(0, 9, eager=True),
...     }
... )
>>> df
shape: (9, 2)
┌──────┬──────┐
│ col1 ┆ col2 │
│ ---  ┆ ---  │
│ str  ┆ i64  │
╞══════╪══════╡
│ A    ┆ 0    │
│ B    ┆ 1    │
│ C    ┆ 2    │
│ D    ┆ 3    │
│ …    ┆ …    │
│ F    ┆ 5    │
│ G    ┆ 6    │
│ H    ┆ 7    │
│ I    ┆ 8    │
└──────┴──────┘
>>> df.unstack(step=3, how="vertical")
shape: (3, 6)
┌────────┬────────┬────────┬────────┬────────┬────────┐
│ col1_0 ┆ col1_1 ┆ col1_2 ┆ col2_0 ┆ col2_1 ┆ col2_2 │
│ ---    ┆ ---    ┆ ---    ┆ ---    ┆ ---    ┆ ---    │
│ str    ┆ str    ┆ str    ┆ i64    ┆ i64    ┆ i64    │
╞════════╪════════╪════════╪════════╪════════╪════════╡
│ A      ┆ D      ┆ G      ┆ 0      ┆ 3      ┆ 6      │
│ B      ┆ E      ┆ H      ┆ 1      ┆ 4      ┆ 7      │
│ C      ┆ F      ┆ I      ┆ 2      ┆ 5      ┆ 8      │
└────────┴────────┴────────┴────────┴────────┴────────┘
>>> df.unstack(step=3, how="horizontal")
shape: (3, 6)
┌────────┬────────┬────────┬────────┬────────┬────────┐
│ col1_0 ┆ col1_1 ┆ col1_2 ┆ col2_0 ┆ col2_1 ┆ col2_2 │
│ ---    ┆ ---    ┆ ---    ┆ ---    ┆ ---    ┆ ---    │
│ str    ┆ str    ┆ str    ┆ i64    ┆ i64    ┆ i64    │
╞════════╪════════╪════════╪════════╪════════╪════════╡
│ A      ┆ B      ┆ C      ┆ 0      ┆ 1      ┆ 2      │
│ D      ┆ E      ┆ F      ┆ 3      ┆ 4      ┆ 5      │
│ G      ┆ H      ┆ I      ┆ 6      ┆ 7      ┆ 8      │
└────────┴────────┴────────┴────────┴────────┴────────┘