daft.functions.length#

def length(expr: Expression) -> Expression:
    """Retrieves the length of the given expression.

    Args:
        expr (List or Binary or String Expression): expression to compute the length of.

    The behavior depends on the input type:
    - For strings, returns the number of characters.
    - For binary, returns the number of bytes.
    - For lists, returns the number of elements.

    Returns:
        Expression (UInt64 Expression): an expression with the length

    Examples:
        String length:
        >>> import daft
        >>> from daft.functions import length
        >>>
        >>> df = daft.from_pydict({"x": ["foo", "bar", None]})
        >>> df = df.select(length(df["x"]))
        >>> df.show()
        ╭────────╮
        │ x      │
        │ ---    │
        │ UInt64 │
        ╞════════╡
        │ 3      │
        ├╌╌╌╌╌╌╌╌┤
        │ 3      │
        ├╌╌╌╌╌╌╌╌┤
        │ None   │
        ╰────────╯
        <BLANKLINE>
        (Showing first 3 of 3 rows)

        Binary length:
        >>> df = daft.from_pydict({"x": [b"foo", b"bar", None]})
        >>> df = df.select(length(df["x"]))
        >>> df.show()
        ╭────────╮
        │ x      │
        │ ---    │
        │ UInt64 │
        ╞════════╡
        │ 3      │
        ├╌╌╌╌╌╌╌╌┤
        │ 3      │
        ├╌╌╌╌╌╌╌╌┤
        │ None   │
        ╰────────╯
        <BLANKLINE>
        (Showing first 3 of 3 rows)

        List length:
        >>> df = daft.from_pydict({"x": [[1, 2, 3], [4, 5], None]})
        >>> df = df.select(length(df["x"]))
        >>> df.show()
        ╭────────╮
        │ x      │
        │ ---    │
        │ UInt64 │
        ╞════════╡
        │ 3      │
        ├╌╌╌╌╌╌╌╌┤
        │ 2      │
        ├╌╌╌╌╌╌╌╌┤
        │ None   │
        ╰────────╯
        <BLANKLINE>
        (Showing first 3 of 3 rows)
    """
    return Expression._call_builtin_scalar_fn("length", expr)