polars.Expr.arr.join#

Expr.arr.join(separator: IntoExprColumn, *, ignore_nulls: bool = True) → Expr[source]#

Join all string items in a sub-array and place a separator between them.

This errors if inner type of array != String.

Parameters:

separator

string to separate the items with

ignore_nulls

Ignore null values (default).

If set to False, null values will be propagated. If the sub-list contains any null values, the output is None.

Returns:

Expr: Expression of data type String.

Examples

>>> df = pl.DataFrame(
...     {"s": [["a", "b"], ["x", "y"]], "separator": ["*", "_"]},
...     schema={
...         "s": pl.Array(pl.String, 2),
...         "separator": pl.String,
...     },
... )
>>> df.with_columns(join=pl.col("s").arr.join(pl.col("separator")))
shape: (2, 3)
┌───────────────┬───────────┬──────┐
│ s             ┆ separator ┆ join │
│ ---           ┆ ---       ┆ ---  │
│ array[str, 2] ┆ str       ┆ str  │
╞═══════════════╪═══════════╪══════╡
│ ["a", "b"]    ┆ *         ┆ a*b  │
│ ["x", "y"]    ┆ _         ┆ x_y  │
└───────────────┴───────────┴──────┘