[Tutor] getting the size of an open TarFile object

[Adam A. Zajac]

Hello all,

I've been working with the tarfile module and just noticed an apparent
flaw in my own logic.  I wanted to add files to the tar until it neared
a certain file size.  After every addition I would use
os.path.getsize().  What I noticed today is that I could add a file to
the tar without the tar's size changing.  I'm assuming that because the
TarFile object is not closed, finding its size that way isn't reliable.

The first thing I tried was using flush(), but TarFile objects
apparently don't do that.  I also can't close the object and reopen it
for appending because TarFile objects can't append if the tar is
compressed.  And finally, I can't predict the compression ratio, so I
can't merely keep track of the size of the individual files without a
huge gap to my target size.

I'm giving up on it for the night.  Anyone have any thoughts?

Adam