This is on Windows 7 SP1.  Run 'chcp 65001' then Python from a console.  Note the extra characters when non-ASCII characters are in the string.  At a guess it appears to be using the UTF-8 byte length of the internal representation instead of the character count.

Python 3.3.0a1 (default, Mar  4 2012, 17:27:59) [MSC v.1500 32 bit (Intel)] on win32
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>>> print('hello')
hello
>>> print('p\u012bny\u012bn')
pīnyīn
n
>>> print('\u012b'*10)
īīīīīīīīīī
�īīīī
�ī