Multiply within a group in polars

I would like to take the product within a group in polars

The following works but I suspect there is a more elegant/efficient way to perform this operation. Thank you

import polars as pl
import numpy as np

D = pl.DataFrame({'g':['a','a','b','b'],'v':[1,2,3,4],'v2':[2,3,4,5]})
D.group_by('g').agg(pl.all().map_elements(
                        lambda group: np.prod(group.to_numpy()),return_dtype=pl.Float64))

>Solution :

You could use Expr.product:

D.group_by('g').agg(pl.all().product())

Output:

┌─────┬─────┬─────┐
│ g   ┆ v   ┆ v2  │
│ --- ┆ --- ┆ --- │
│ str ┆ i64 ┆ i64 │
╞═════╪═════╪═════╡
│ b   ┆ 12  ┆ 20  │
│ a   ┆ 2   ┆ 6   │
└─────┴─────┴─────┘

If you want Floats:

D.group_by('g').agg(pl.all().product().cast(pl.Float64))

┌─────┬──────┬──────┐
│ g   ┆ v    ┆ v2   │
│ --- ┆ ---  ┆ ---  │
│ str ┆ f64  ┆ f64  │
╞═════╪══════╪══════╡
│ b   ┆ 12.0 ┆ 20.0 │
│ a   ┆ 2.0  ┆ 6.0  │
└─────┴──────┴──────┘