StringIO cStringIO

Python的StringIO库用于实现在内存缓冲区读写文件，看官方对StringIO的介绍，第一句话就是：The module implements file-like class, StingIO,
that reads and writes a string buffer(also known as memory files)

cStringIO和StringIO用法相同，速度更快，常常这样使用：

try:
import cStringIO as StringIO
except ImportError:
import StringIO
>>> output = StringIO.StringIO()
>>> output.write('At that time, I was afraid')
>>> output
<cStringIO.StringO object at 0x7fba35ffaed8>
>>> print output.getvalue()
At that time, I was afraid
>>> output.close()

但cStringIO.StringIO不能作为基类被继承；2. 创建cStringIO.StringIO对象时，如果初始化函数提供了初始化数据，新生成的对象是只读的。

>>> o2 = cStringIO.StringIO('initialization string')
>>> print o2.getvalue()
initialization string
>>> o2.write('write string')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'cStringIO.StringI' object has no attribute 'write'