Index: Lib/codecs.py
===================================================================
--- Lib/codecs.py	(revision 77138)
+++ Lib/codecs.py	(working copy)
@@ -858,10 +858,15 @@
 parameter.
 
 """
- if encoding is not None and \
- 'b' not in mode:
- # Force opening of the file in binary mode
- mode = mode + 'b'
+ if encoding is not None:
+ if 'U' in mode:
+ # No automatic conversion of '\n' is done on reading and writing
+ mode = mode.strip().replace('U', '')
+ if mode[:1] not in set('rwa'):
+ mode = 'r' + mode
+ if 'b' not in mode:
+ # Force opening of the file in binary mode
+ mode = mode + 'b'
 file = __builtin__.open(filename, mode, buffering)
 if encoding is None:
 return file
Index: Lib/test/test_codecs.py
===================================================================
--- Lib/test/test_codecs.py	(revision 77138)
+++ Lib/test/test_codecs.py	(working copy)
@@ -3,6 +3,8 @@
 import codecs
 import sys, StringIO, _testcapi
 
+from test.test_support import TESTFN, unlink
+
 class Queue(object):
 """
 queue: write bytes at one end, read bytes from the other end
@@ -437,6 +439,21 @@
 def test_errors(self):
 self.assertRaises(UnicodeDecodeError, codecs.utf_16_decode, "\xff", "strict", True)
 
+ def test_bug691291(self):
+ # Files are always opened in binary mode, even if no binary mode was
+ # specified. This means that no automatic conversion of '\n' is done
+ # on reading and writing.
+ s1 = u'Hello\r\nworld\r\n'
+
+ s = s1.encode(self.encoding)
+ try:
+ with open(TESTFN, 'wb') as fp:
+ fp.write(s)
+ with codecs.open(TESTFN, 'U', encoding=self.encoding) as reader:
+ self.assertEqual(reader.read(), s1)
+ finally:
+ unlink(TESTFN)
+
 class UTF16LETest(ReadTest):
 encoding = "utf-16-le"
 
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