It seems the documentation is not enough accurate.

"Unlike the StringIO module, this module is not able to accept Unicode strings that cannot be encoded as plain ASCII strings."

I understand that u'foo' can be encoded as plan ASCII, however it does not behave correctly with cStringIO.


Python 2.7.3 (default, Apr 14 2012, 01:49:35) 
>>> from cStringIO import StringIO
>>> StringIO(u'foo').read()
'f\x00o\x00o\x00'
>>>