$ cat git.tar | /usr/bin/python3  foo3.py
$ cat git.tar | /usr/bin/python3  foo3.py
Traceback (most recent call last):
  File "foo3.py", line 5, in <module>
    tar.extractall("tarout")
  File "/usr/lib/python3.4/tarfile.py", line 1980, in extractall
    self.extract(tarinfo, path, set_attrs=not tarinfo.isdir())
  File "/usr/lib/python3.4/tarfile.py", line 2019, in extract
    set_attrs=set_attrs)
  File "/usr/lib/python3.4/tarfile.py", line 2088, in _extract_member
    self.makefile(tarinfo, targetpath)
  File "/usr/lib/python3.4/tarfile.py", line 2127, in makefile
    source.seek(tarinfo.offset_data)
  File "/usr/lib/python3.4/tarfile.py", line 518, in seek
    raise StreamError("seeking backwards is not allowed")
tarfile.StreamError: seeking backwards is not allowed
$ cat zip.tar | /usr/bin/python3  foo3.py
$ cat zip.tar | /usr/bin/python3  foo3.py
Traceback (most recent call last):
  File "/usr/lib/python3.4/tarfile.py", line 2177, in makelink
    os.symlink(tarinfo.linkname, targetpath)
FileExistsError: [Errno 17] File exists: 'CHANGES.gz' -> 'tarout/usr/share/doc/zip/changelog.gz'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "foo3.py", line 5, in <module>
    tar.extractall("tarout")
  File "/usr/lib/python3.4/tarfile.py", line 1980, in extractall
    self.extract(tarinfo, path, set_attrs=not tarinfo.isdir())
  File "/usr/lib/python3.4/tarfile.py", line 2019, in extract
    set_attrs=set_attrs)
  File "/usr/lib/python3.4/tarfile.py", line 2096, in _extract_member
    self.makelink(tarinfo, targetpath)
  File "/usr/lib/python3.4/tarfile.py", line 2188, in makelink
    targetpath)
  File "/usr/lib/python3.4/tarfile.py", line 2088, in _extract_member
    self.makefile(tarinfo, targetpath)
  File "/usr/lib/python3.4/tarfile.py", line 2127, in makefile
    source.seek(tarinfo.offset_data)
  File "/usr/lib/python3.4/tarfile.py", line 518, in seek
    raise StreamError("seeking backwards is not allowed")
tarfile.StreamError: seeking backwards is not allowed