daft.functions.regexp_extract#

def regexp_extract(expr: Expression, pattern: str | Expression, index: int = 0) -> Expression:
    r"""Extracts the specified match group from the first regex match in each string in a string column.

    Args:
        expr: String expression to extract from
        pattern: The regex pattern to extract
        index: The index of the regex match group to extract

    Returns:
        Expression: a String expression with the extracted regex match

    Note:
        If index is 0, the entire match is returned.
        If the pattern does not match or the group does not exist, a null value is returned.

    Examples:
        >>> import daft
        >>> from daft.functions import regexp_extract
        >>>
        >>> regex = r"(\d)(\d*)"
        >>> df = daft.from_pydict({"x": ["123-456", "789-012", "345-678"]})
        >>> df.with_column("match", regexp_extract(df["x"], regex)).collect()
        ╭─────────┬────────╮
        │ x       ┆ match  │
        │ ---     ┆ ---    │
        │ String  ┆ String │
        ╞═════════╪════════╡
        │ 123-456 ┆ 123    │
        ├╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┤
        │ 789-012 ┆ 789    │
        ├╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┤
        │ 345-678 ┆ 345    │
        ╰─────────┴────────╯
        <BLANKLINE>
        (Showing first 3 of 3 rows)

        Extract the first capture group

        >>> df.with_column("match", regexp_extract(df["x"], regex, 1)).collect()
        ╭─────────┬────────╮
        │ x       ┆ match  │
        │ ---     ┆ ---    │
        │ String  ┆ String │
        ╞═════════╪════════╡
        │ 123-456 ┆ 1      │
        ├╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┤
        │ 789-012 ┆ 7      │
        ├╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌┤
        │ 345-678 ┆ 3      │
        ╰─────────┴────────╯
        <BLANKLINE>
        (Showing first 3 of 3 rows)


    Tip: See Also
        [`regexp_extract_all`](https://docs.daft.ai/en/stable/api/functions/regexp_extract_all/)
    """
    return Expression._call_builtin_scalar_fn("regexp_extract", expr, pattern, index)