The current version of PL/Python
   functions as a trusted language only; access to the file system and
   other local resources is disabled.  Specifically,
   PL/Python uses the Python restricted
   execution environment, further restricts it to prevent the use of
   the file open call, and allows only modules from a
   specific list to be imported.  Presently, that list includes:
   array, bisect, binascii,
   calendar, cmath, codecs,
   errno, marshal, math, md5,
   mpz, operator, pcre,
   pickle, random, re, regex,
   sre, sha, string, StringIO,
   struct, time, whrandom, and
   zlib.