codec.StreamReaderWriter: issues with interlaced read-write #56722

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1. vstinner commented on Jul 7, 2011

   

   vstinner

   on Jul 7, 2011

   MemberAuthor

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   The following test fails with an AssertionError('a' != 'b') on the first read.

   import codecs
   
   FILENAME = 'test'
   
   with open(FILENAME, 'wb') as f:
       f.write('abcd'.encode('utf-8'))
   with codecs.open(FILENAME, 'r+', encoding='utf-8') as f:
       f.write("1")
   
       pos = f.writer.tell()
       assert pos == 1, "writer pos: %s != 1" % pos
       pos = f.reader.tell()
       assert pos == 1, "reader pos: %s != 1" % pos
       pos = f.stream.tell()
       assert pos == 1, "stream pos: %s != 1" % pos
   
       # read() must call writer.flush()
       char = f.read(1)
       assert char == 'b', "%r != 'b'" % (char,)
       # write() must rewind the raw stream
       f.write('3')
       tail = f.read()
       assert tail == 'd', "%r != 'd'" % (tail,)
       f.flush()
       with open(FILENAME, 'rb') as f:
           assert f.read() == b'1b3d'

   I suppose that readline(), readlines() and __next__() have also issues.

   See also issue bpo-12215: similar issue with io.TextIOWrapper.
2. vstinner

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-unicode

   on Jul 7, 2011
3. BreamoreBoy commented on Jul 3, 2014

   

   BreamoreBoymannequin

   on Jul 3, 2014

   Mannequin

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   Codecs gurus FYI.
4. BreamoreBoy

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Jul 3, 2014
5. vstinner commented on Jun 28, 2017

   

   vstinner

   on Jun 28, 2017

   MemberAuthor

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   Sorry, I just lost track of this issue and so will just close it. Moreover, I also closed bpo-12215.
6. vstinner

   closed this as completedon Jun 28, 2017
7. ezio-melotti

   transferred this issue fromon Apr 10, 2022