polars.Expr.list.join#

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

Join all string items in a sublist and place a separator between them.

This errors if inner type of list != 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", "c"], ["x", "y"]]})
>>> df.with_columns(join=pl.col("s").list.join(" "))
shape: (2, 2)
┌─────────────────┬───────┐
│ s               ┆ join  │
│ ---             ┆ ---   │
│ list[str]       ┆ str   │
╞═════════════════╪═══════╡
│ ["a", "b", "c"] ┆ a b c │
│ ["x", "y"]      ┆ x y   │
└─────────────────┴───────┘

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