util.py 文件源码

def record(*fields):
    """Constructs a type that can be extended to create immutable, value types.

    Examples:
        A typical declaration looks like::

            class MyRecord(record('a', ('b', 1))):
                pass

        The above would make a sub-class of ``collections.namedtuple`` that was named ``MyRecord`` with
        a constructor that had the ``b`` field set to 1 by default.

    Note:
        This uses meta-class machinery to rewrite the inheritance hierarchy.
        This is done in order to make sure that the underlying ``namedtuple`` instance is
        bound to the right type name and to make sure that the synthetic class that is generated
        to enable this machinery is not enabled for sub-classes of a user's record class.

    Args:
        fields (list[str | (str, any)]): A sequence of str or pairs that
    """
    @six.add_metaclass(_RecordMetaClass)
    class RecordType(object):
        _record_sentinel = True
        _record_fields = fields

    return RecordType