[ python-Bugs-1527974 ] tarfile chokes on ipython archive on Windows

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Bugs item #1527974, was opened at 2006-07-24 23:00
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Arve Knudsen (arve_knudsen)
Assigned to: Nobody/Anonymous (nobody)
Summary: tarfile chokes on ipython archive on Windows

Initial Comment:
I'm trying to extract files from the latest ipython tar
archive, available from
http://ipython.scipy.org/dist/ipython-0.7.2.tar.gz,
using tarfile. This is on Windows XP, using Python
2.4.3. There is only a problem if I open the archive in
stream mode (the "mode" argument to tarfile.open is
"r|gz"), in which case tarfile raises StreamError. I'd
be happy if this error could be sorted out.

The following script should trigger the error:

import tarfile

f = file(r"ipython-0.7.2.tar.gz", "rb")
tar = tarfile.open(fileobj=f, mode="r|gz")
try:
    for m in tar:
        tar.extract(m)
finally:
    tar.close()
    f.close(

The resulting exception:
Traceback (most recent call last):
  File "tst.py", line 7, in ?
    tar.extract(m)
  File "C:\Program Files\Python24\lib\tarfile.py", line
1335, in extract
    self._extract_member(tarinfo, os.path.join(path,
tarinfo.name))
  File "C:\Program Files\Python24\lib\tarfile.py", line
1431, in _extract_member

    self.makelink(tarinfo, targetpath)
  File "C:\Program Files\Python24\lib\tarfile.py", line
1515, in makelink
    self._extract_member(self.getmember(linkpath),
targetpath)
  File "C:\Program Files\Python24\lib\tarfile.py", line
1423, in _extract_member

    self.makefile(tarinfo, targetpath)
  File "C:\Program Files\Python24\lib\tarfile.py", line
1461, in makefile
    copyfileobj(source, target)
  File "C:\Program Files\Python24\lib\tarfile.py", line
158, in copyfileobj
    shutil.copyfileobj(src, dst)
  File "C:\Program Files\Python24\lib\shutil.py", line
22, in copyfileobj
    buf = fsrc.read(length)
  File "C:\Program Files\Python24\lib\tarfile.py", line
551, in _readnormal
    self.fileobj.seek(self.offset + self.pos)
  File "C:\Program Files\Python24\lib\tarfile.py", line
420, in seek
    raise StreamError, "seeking backwards is not allowed"
tarfile.StreamError: seeking backwards is not allowed

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