Class Flag

Lib/enum.py:1428–1660

Support for flags

class Flag(Enum, boundary=STRICT):
    """
    Support for flags
    """

    _numeric_repr_ = repr

    @staticmethod
    def _generate_next_value_(name, start, count, last_values):
        """
        Generate the next value when not given.

        name: the name of the member
        start: the initial start value or None
        count: the number of existing members
        last_values: the last value assigned or None
        """
        if not count:
            return start if start is not None else 1
        last_value = max(last_values)
        try:
            high_bit = _high_bit(last_value)
        except Exception:
            raise TypeError('invalid flag value %r' % last_value) from None
        return 2 ** (high_bit+1)

    @classmethod
    def _iter_member_by_value_(cls, value):
        """
        Extract all members from the value in definition (i.e. increasing value) order.
        """
        for val in _iter_bits_lsb(value & cls._flag_mask_):
            yield cls._value2member_map_.get(val)

    _iter_member_ = _iter_member_by_value_

    @classmethod
    def _iter_member_by_def_(cls, value):
        """
        Extract all members from the value in definition order.
        """
        yield from sorted(
                cls._iter_member_by_value_(value),
                key=lambda m: m._sort_order_,
                )

    @classmethod
    def _missing_(cls, value):
        """
        Create a composite member containing all canonical members present in `value`.

        If non-member values are present, result depends on `_boundary_` setting.
        """
        if not isinstance(value, int):
            raise ValueError(
                    "%r is not a valid %s" % (value, cls.__qualname__)
                    )
        # check boundaries