TypeError:描述符“write”需要'_拜特西奥'对象，但收到'str'

Question

我使用Python pickling来序列化数据并写入流。 （然后从流中读取 代码如下：

import pickle
import io
import pprint

class SimpleObject:

    def __init__(self, name):
        self.name = name
        self.name_backwards = name[::-1]


data = []
data.append(SimpleObject('pickle'))
data.append(SimpleObject('preserve'))
data.append(SimpleObject('last'))

print (type(data))

# simulate a file
out_s = io.BytesIO

print (type(out_s))

for o in data:
    print('WRITING : {} ({})'.format(o.name, o.name_backwards))
    # writing to the stream
    print (type(o))
    pickle.dump(o, out_s)
    out_s.flush() 

写入流时出错-

^{pr2}$

当我打印类型（o）时，它将其打印为（SimpleObject的）实例

WRITING : pickle (elkcip)
<type 'instance'>

那么，为什么会出现此错误？如何修复？在