docutils/_compat.py

   1 # $Id$
   2 # Author: Georg Brandl <georg@python.org>
   3 # Copyright: This module has been placed in the public domain.
   4
   5 """
   6 Python 2/3 compatibility definitions.
   7
   8 This module currently provides the following helper symbols:
   9
  10 * bytes (name of byte string type; str in 2.x, bytes in 3.x)
  11 * b (function converting a string literal to an ASCII byte string;
  12   can be also used to convert a Unicode string into a byte string)
  13 * u_prefix (unicode repr prefix, 'u' in 2.x, nothing in 3.x)
  14 * BytesIO (a StringIO class that works with bytestrings)
  15 """
  16
  17 import sys
  18
  19 if sys.version_info < (3,0):
  20     b = bytes = str
  21     u_prefix = 'u'
  22     from StringIO import StringIO as BytesIO
  23 else:
  24     import builtins
  25     bytes = builtins.bytes
  26     u_prefix = ''
  27     def b(s):
  28         if isinstance(s, str):
  29             return s.encode('latin1')
  30         elif isinstance(s, bytes):
  31             return s
  32         else:
  33             raise TypeError("Invalid argument %r for b()" % (s,))
  34     # using this hack since 2to3 "fixes" the relative import
  35     # when using ``from io import BytesIO``
  36     BytesIO = __import__('io').BytesIO