schema.dump和schema.load
schema.dump()方法返回一个MarshResult的对象，marshmallow官方API说dump和load方法返回的都是dict对象，但查看源码，MarshResult对象是一个namedtuple.
## marshmallow::schema.py ### line 25 #### #: Return type of :meth:`Schema.dump` including serialized data and errors
MarshalResult = namedtuple('MarshalResult', ['data', 'errors'])
#: Return type of :meth:`Schema.load`, including deserialized data and errors
UnmarshalResult = namedtuple('UnmarshalResult', ['data', 'errors'])
我在跑官方Example的时候，这里是有问题的
try:
data = quote_schema.load(json_data)
except ValidationError as err:
return jsonify(err.messages), 422
first, last = data['author']['first'], data['author']['last'] # 此处代码报错， TypeError: tuple indices must be integers or slices, not str
namedtuple通过result['data']['xxx']的方法无法访问对象信息
但是通过result.data['xxx']却是OK的。Python Doc里对namedtuple的问方式也是"."访问。好像可以理解为name是namedtuple的一个attribute，
>>> # Basic example
>>> Point = namedtuple('Point', ['x', 'y'])
>>> p = Point(11, y=22) # instantiate with positional or keyword arguments
>>> x, y = p # unpack like a regular tuple
>>> x, y
(11, 22)
>>> p.x + p.y # fields also accessible by name
33
>>> p # readable __repr__ with a name=value style
Point(x=11, y=22)