Class crontab_parser

celery/schedules.py:196–320

Parser for Crontab expressions. Any expression of the form 'groups' (see BNF grammar below) is accepted and expanded to a set of numbers. These numbers represent the units of time that the Crontab needs to run on: .. code-block:: bnf digit :: '0'..'9' dow

class crontab_parser:
    """Parser for Crontab expressions.

    Any expression of the form 'groups'
    (see BNF grammar below) is accepted and expanded to a set of numbers.
    These numbers represent the units of time that the Crontab needs to
    run on:

    .. code-block:: bnf

        digit   :: '0'..'9'
        dow     :: 'a'..'z'
        number  :: digit+ | dow+
        steps   :: number
        range   :: number ( '-' number ) ?
        numspec :: '*' | range
        expr    :: numspec ( '/' steps ) ?
        groups  :: expr ( ',' expr ) *

    The parser is a general purpose one, useful for parsing hours, minutes and
    day of week expressions.  Example usage:

    .. code-block:: pycon

        >>> minutes = crontab_parser(60).parse('*/15')
        [0, 15, 30, 45]
        >>> hours = crontab_parser(24).parse('*/4')
        [0, 4, 8, 12, 16, 20]
        >>> day_of_week = crontab_parser(7).parse('*')
        [0, 1, 2, 3, 4, 5, 6]

    It can also parse day of month and month of year expressions if initialized
    with a minimum of 1.  Example usage:

    .. code-block:: pycon

        >>> days_of_month = crontab_parser(31, 1).parse('*/3')
        [1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31]
        >>> months_of_year = crontab_parser(12, 1).parse('*/2')
        [1, 3, 5, 7, 9, 11]
        >>> months_of_year = crontab_parser(12, 1).parse('2-12/2')
        [2, 4, 6, 8, 10, 12]

    The maximum possible expanded value returned is found by the formula:

        :math:`max_ + min_ - 1`
    """

    ParseException = ParseException

    _range = r'(\w+?)-(\w+)'
    _steps = r'/(\w+)?'
    _star = r'\*'

    def __init__(self, max_: int = 60, min_: int = 0):
        self.max_ = max_
        self.min_ = min_
        self.pats: tuple[tuple[re.Pattern, Callable], ...] = (