python: int to unicode string

>>> import types
>>> print type(str(2))
<type 'str'>
>>> print type(str('2'))
<type 'str'>

# 这里先转为str，在转为unicode
>>> print type(str(2).decode('utf-8'))
<type 'unicode'>
>>> print type(str('32').decode('utf-8'))
<type 'unicode'>
>>> print str(2).decode('utf-8')
2