daft.functions.list_filter#

def list_filter(list_expr: Expression, predicate: Expression) -> Expression:
    """Filters elements in a list using a boolean predicate expression.

    Elements where the predicate evaluates to `False` or `null` are removed.
    Null list rows remain null. Empty list rows remain empty.

    Args:
        list_expr (List Expression): expression to filter.
        predicate: Boolean expression to evaluate on each element. Use `daft.element()` to reference the current element.

    Returns:
        Expression (List Expression): an expression representing the filtered list.

    Examples:
        >>> import daft
        >>> from daft.functions import list_filter
        >>> df = daft.from_pydict({"letters": [["a", "b", "a"], ["b", "c", "b", "c"]]})
        >>> df.with_column("no_b", list_filter(df["letters"], daft.element() != "b")).collect()
        ╭──────────────┬──────────────╮
        │ letters      ┆ no_b         │
        │ ---          ┆ ---          │
        │ List[String] ┆ List[String] │
        ╞══════════════╪══════════════╡
        │ [a, b, a]    ┆ [a, a]       │
        ├╌╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌╌╌┤
        │ [b, c, b, c] ┆ [c, c]       │
        ╰──────────────┴──────────────╯
        <BLANKLINE>
        (Showing first 2 of 2 rows)
    """
    return Expression._call_builtin_scalar_fn("list_filter", list_expr, predicate)