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, '' in 3.x)
  14   (Required in docutils/test/test_publisher.py)
  15 * BytesIO (a StringIO class that works with bytestrings)
  16 """
  17
  18 import sys
  19
  20 if sys.version_info < (3,0):
  21     b = bytes = str
  22     u_prefix = 'u'
  23     from StringIO import StringIO as BytesIO
  24 else:
  25     import builtins
  26     bytes = builtins.bytes
  27     u_prefix = ''
  28     def b(s):
  29         if isinstance(s, str):
  30             return s.encode('latin1')
  31         elif isinstance(s, bytes):
  32             return s
  33         else:
  34             raise TypeError("Invalid argument %r for b()" % (s,))
  35     # using this hack since 2to3 "fixes" the relative import
  36     # when using ``from io import BytesIO``
  37     BytesIO = __import__('io').BytesIO
  38
  39 if sys.version_info < (2,5):
  40     import __builtin__
  41
  42     def __import__(name, globals={}, locals={}, fromlist=[], level=-1):
  43         """Compatibility definition for Python 2.4.
  44
  45         Silently ignore the `level` argument missing in Python < 2.5.
  46         """
  47         # we need the level arg because the default changed in Python 3.3
  48         return __builtin__.__import__(name, globals, locals, fromlist)