polars.Expr.cum_count#
- Expr.cum_count(*, reverse: bool = False) Expr [source]#
Return the cumulative count of the non-null values in the column.
- Parameters:
- reverse
Reverse the operation.
Examples
>>> df = pl.DataFrame({"a": ["x", "k", None, "d"]}) >>> df.with_columns( ... pl.col("a").cum_count().alias("cum_count"), ... pl.col("a").cum_count(reverse=True).alias("cum_count_reverse"), ... ) shape: (4, 3) ┌──────┬───────────┬───────────────────┐ │ a ┆ cum_count ┆ cum_count_reverse │ │ --- ┆ --- ┆ --- │ │ str ┆ u32 ┆ u32 │ ╞══════╪═══════════╪═══════════════════╡ │ x ┆ 1 ┆ 3 │ │ k ┆ 2 ┆ 2 │ │ null ┆ 2 ┆ 1 │ │ d ┆ 3 ┆ 1 │ └──────┴───────────┴───────────────────┘