polars.Expr.agg_groups

Expr.agg_groups() → Expr

Get the group indexes of the group by operation.

Deprecated since version 1.35: use df.with_row_index().group_by(...).agg(pl.col('index')) instead. This method will be removed in Polars 2.0.

Should be used in aggregation context only.

Examples

>>> import warnings
>>> warnings.filterwarnings("ignore", category=DeprecationWarning)
>>> df = pl.DataFrame(
...     {
...         "group": [
...             "one",
...             "one",
...             "one",
...             "two",
...             "two",
...             "two",
...         ],
...         "value": [94, 95, 96, 97, 97, 99],
...     }
... )
>>> df.group_by("group", maintain_order=True).agg(pl.col("value").agg_groups())
shape: (2, 2)
┌───────┬───────────┐
│ group ┆ value     │
│ ---   ┆ ---       │
│ str   ┆ list[u32] │
╞═══════╪═══════════╡
│ one   ┆ [0, 1, 2] │
│ two   ┆ [3, 4, 5] │
└───────┴───────────┘

New recommended approach: >>> ( … df.with_row_index() … .group_by(“group”, maintain_order=True) … .agg(pl.col(“index”)) … ) shape: (2, 2) ┌───────┬───────────┐ │ group ┆ index │ │ — ┆ — │ │ str ┆ list[u32] │ ╞═══════╪═══════════╡ │ one ┆ [0, 1, 2] │ │ two ┆ [3, 4, 5] │ └───────┴───────────┘