New submission from Andrzej Mateja <mateja....@gmail.com>:
Since Python 3.9 tarfile.is_tarfile accepts not only paths but also files and
file-like objects (bpo-29435).
Verification if a file or file-like object is a tar file modifies file object's
current position.
Imagine a function listing names of all tar archive members but checking first
if this is a valid tar archive. When its argument is a str or pathlib.Path this
is quite straightforward. If the argument is a file of file-like object then
current position must be reset or TarFile.getmembers() returns empty list.
import tarfile
def list_tar(archive):
if tarfile.is_tarfile(archive):
kwargs = {'fileobj' if hasattr(archive, 'read') else 'name': archive}
t = tarfile.open(**kwargs)
return [member.name for member in t.getmembers()]
return []
if __name__ == '__main__':
path = 'archive.tar.gz'
print(list_tar(path))
print(list_tar(open(path, 'rb')))
['spam.py', 'ham.py', 'bacon.py', 'eggs.py']
[]
----------
components: Library (Lib)
messages: 394922
nosy: mateja.and
priority: normal
severity: normal
status: open
title: tarfile.is_tarfile() modifies file object's current position
type: behavior
versions: Python 3.10, Python 3.11, Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44289>
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