Python 2.5c1 (r25c1:51305, Aug 19 2006, 18:23:29) 
[GCC 4.1.2 20060814 (prerelease) (Debian 4.1.1-11)] on
linux2

(Also seen in 2.4)

shlex.split do not like unicode strings:

>>> shlex.split(u"foo")
['f\x00\x00\x00o\x00\x00\x00o\x00\x00\x00']

The shlex code IMO suggests that it should accept
unicode (as it checks for argument being an instance of
basestring).

Digging slightly into this, this seems to be a
difference between StringIO and cStringIO. While
cStringIO claims it accepts unicode as long as it
encode too ASCII it gives invalid results:

>>> sys.getdefaultencoding()
'ascii'


>>> cStringIO.StringIO(u'foo').getvalue()
'f\x00\x00\x00o\x00\x00\x00o\x00\x00\x00'

Perhaps cStringIO should .encode to ASCII encoding
before consuming the input, as I can't imagine anyone
cares about the above result (which I guess are the
UCS-2 or UCS-4 characters).

Logged In: YES 
user_id=849994

Thanks for your report, this is now fixed in rev. 52301,
52302 (2.5).

Still happens on latest 2.7:

>>> from cStringIO import StringIO
>>> sio = StringIO(u"abc")
>>> sio.getvalue()
'a\x00b\x00c\x00'

And unsurprisingly so, since the fix was reverted in r56830 by Georg.

Georg, is this patch ok to you?

If you think it's fine to change this behavior, then yes :)

New changeset 27ae7d4e1983 by Antoine Pitrou in branch '2.7':
Issue #1548891: The cStringIO.StringIO() constructor now encodes unicode
http://hg.python.org/cpython/rev/27ae7d4e1983

> If you think it's fine to change this behavior, then yes :)

Well, the "documented" behaviour makes no sense.
Either it should raise TypeError or convert. Since write() converts, it's logical for the constructor to do so as well.

New changeset 0b39f2486314 by Éric Araujo in branch '2.7':
Note that the #1548891 fix indirectly fixes shlex (#6988, #1170)
http://hg.python.org/cpython/rev/0b39f2486314