Python version: 2.7.2 (default, Aug 17 2011, 14:44:37) 
[GCC 4.1.2 20080704 (Red Hat 4.1.2-50)]
ctypes version: 1.1.0
string with nulls: x y 
a.b= x
type(a.b) <type 'str'>
buffer contents, the 'y' is not copied:
x 120
  0
  0
  0
  0
  0
  0
  0
  0
  0