attrs.py 文件源码

def sequence_of_type(_type, mutable, instance, attribute, value):
    """
    Validate that a value is a Sequence containing a specific type.

    :arg _type: The type of the values inside of the sequence
    :arg mutable: selects whether a sequence can be mutable or not
        :mutable: only mutable sequences are allowed
        :immutable: only immutable sequences are allowed
        :both: both mutable and immutable sequences are allowed
    :arg instance: The instance of the attr.s class that is being created
    :arg attribute: The attribute of the attr.s class that is being set
    :arg value: The value the attribute is being set to

    This function will be used with the :meth:`attr.ib` validate parameter and
    :func:`functools.partial`.  Example::

        @attr.s
        class CommodityData:
            type = attr.ib(validator=partial(enum_validator, CommodityType))
    """
    if mutable == 'both':
        msg = 'a Sequence'
    elif mutable == 'mutable':
        msg = 'a MutableSequence'
    elif mutable == 'immutable':
        msg = 'an Immutable Sequence'
    else:
        raise ValueError('sequence_of_type was given an improper argument for mutable')

    if not isinstance(value, Sequence):
        raise ValueError('{} is not {}'.format(value, msg))

    if isinstance(value, MutableSequence):
        if mutable == 'immutable':
            raise ValueError('{} is not {}'.format(value, msg))
    else:
        if mutable == 'mutable':
            raise ValueError('{} is not {}'.format(value, msg))

    for entry in value:
        if not isinstance(entry, _type):
            raise ValueError('The Sequence element {} is not a {}'.format(value, _type))