How can I use UUIDs in SQLAlchemy?

Question

Is there a way to define a column (primary key) as a UUID in SQLAlchemy if using PostgreSQL (Postgres)?

Answer 1

In case anyone is interested, I've been using Tom Willis answer, but found useful to add a string to uuid.UUID conversion in the process_bind_param method

class UUID(types.TypeDecorator):
    impl = types.LargeBinary

    def __init__(self):
        self.impl.length = 16
        types.TypeDecorator.__init__(self, length=self.impl.length)

    def process_bind_param(self, value, dialect=None):
        if value and isinstance(value, uuid.UUID):
            return value.bytes
        elif value and isinstance(value, basestring):
            return uuid.UUID(value).bytes
        elif value:
            raise ValueError('value %s is not a valid uuid.UUId' % value)
        else:
            return None

    def process_result_value(self, value, dialect=None):
        if value:
            return uuid.UUID(bytes=value)
        else:
            return None

    def is_mutable(self):
        return False

Answer 2

I've used the UUIDType from the SQLAlchemy-Utils package: http://sqlalchemy-utils.readthedocs.org/en/latest/data_types.html#module-sqlalchemy_utils.types.uuid