expression.py 文件源码

def __init__(self, *args, **kwargs):
        if args and isinstance(args[0], (SelectBase, ScalarSelect)):
            s = args[0]
        else:
            if not args:
                args = ([literal_column('*')],)
            s = select(*args, **kwargs).as_scalar().self_group()

        UnaryExpression.__init__(self, s, operator=operators.exists,
                                  type_=sqltypes.Boolean)