def guess_code(s):
  if isinstance(s, unicode):
    return 'UNICODE'
  for c in ['utf-8', 'euc-jp', 'cp932', 'iso-2022-jp', 'latin-1', 'ascii']:
    try:
      u = s.decode(c)
      return c
    except (UnicodeDecodeError, LookupError):
      continue
    else:
      return 'unknown'

s = os.environ['hoge']
print guess_code(s)
s = cgi.FieldStorage()['hoge']
print guess_code(s)