polars.Expr.cum_prod#

Expr.cum_prod(*, reverse: bool = False) → Self[source]#

Get an array with the cumulative product computed at every element.

Parameters:

reverse: Reverse the operation.

Notes

Dtypes in {Int8, UInt8, Int16, UInt16} are cast to Int64 before summing to prevent overflow issues.

Examples

>>> df = pl.DataFrame({"a": [1, 2, 3, 4]})
>>> df.with_columns(
...     pl.col("a").cum_prod().alias("cum_prod"),
...     pl.col("a").cum_prod(reverse=True).alias("cum_prod_reverse"),
... )
shape: (4, 3)
┌─────┬──────────┬──────────────────┐
│ a   ┆ cum_prod ┆ cum_prod_reverse │
│ --- ┆ ---      ┆ ---              │
│ i64 ┆ i64      ┆ i64              │
╞═════╪══════════╪══════════════════╡
│ 1   ┆ 1        ┆ 24               │
│ 2   ┆ 2        ┆ 24               │
│ 3   ┆ 6        ┆ 12               │
│ 4   ┆ 24       ┆ 4                │
└─────┴──────────┴──────────────────┘