polars.Expr.list.first

Expr.list.first() → Expr

Get the first value of the sublists.

Examples

>>> df = pl.DataFrame({"a": [[3, 2, 1], [], [1, 2]]})
>>> df.with_columns(first=pl.col("a").list.first())
shape: (3, 2)
┌───────────┬───────┐
│ a         ┆ first │
│ ---       ┆ ---   │
│ list[i64] ┆ i64   │
╞═══════════╪═══════╡
│ [3, 2, 1] ┆ 3     │
│ []        ┆ null  │
│ [1, 2]    ┆ 1     │
└───────────┴───────┘