polars.Expr.arr.first

Expr.arr.first() → Expr

Get the first value of the sub-arrays.

Examples

>>> df = pl.DataFrame(
...     {"a": [[1, 2, 3], [4, 5, 6], [7, 8, 9]]},
...     schema={"a": pl.Array(pl.Int32, 3)},
... )
>>> df.with_columns(first=pl.col("a").arr.first())
shape: (3, 2)
┌───────────────┬───────┐
│ a             ┆ first │
│ ---           ┆ ---   │
│ array[i32, 3] ┆ i32   │
╞═══════════════╪═══════╡
│ [1, 2, 3]     ┆ 1     │
│ [4, 5, 6]     ┆ 4     │
│ [7, 8, 9]     ┆ 7     │
└───────────────┴───────┘