gistfile1.txt

Python 2.7.3 (default, Jan  2 2013, 16:53:07) 
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> s = "foo"
>>> type(s)
<type 'str'>
>>> class mys(str) :
...     i = 4;
... 
>>> type(s)
<type 'str'>
>>> s1 = mys("o hai")
>>> type(s1)
<class '__main__.mys'>
>>> s2 = s1.upper()
>>> s2
'O HAI'
>>> type(s2)
<type 'str'>
>>>