ctypes short string shenannigans

>>> >>> >>> 42105668 >>> 42105668 >>> 'f' >>> 'ab' >>> 'f'

import ctypes b_char = 'b' ctypes.pythonapi.PyString_AsString(id(b_char)) ctypes.memset(_, ord('f'), 1) b_char 'ab' 'ab'[1:]

Single character strings are interned in a special array in CPython.  This means mutation to the internals of a single character string will have global consequences.

(http://www.laurentluce.com/posts/python-string-objects-implementation/ has more information.)