Hello all,

I am testing some logic to handle a user uploading a TAR file. When I feed a blank file to tarfile.is_tarfile() it returns True, which is not what I am expecting:

$ touch tartest
$ cat tartest
$ python -c "import tarfile; print tarfile.is_tarfile('tartest')"
True

If I add some text to the file, it returns False, which I am expecting:

$ echo "not a tar" > tartest
$ python -c "import tarfile; print tarfile.is_tarfile('tartest')"
False

I could add a check at the beginning to check for a zero-length file, but based on the documentation for tarfile.is_tarfile(name) I think this is unecessary:

Return True if name is a tar archive file, that the tarfile module can read.

I went so far as to check the source, tarfile.py, and I can see that it is checking header blocks but I do not fully understand how it is evaluating those blocks.

Am I misreading the documentation and therefore setting unfair expectations?

Thank you,
Zachary