Use python tarfile add without normpath being applied to arcname

I'm using python's tarfile library to create a gzipped tar file.

The tar file needs to have absolute pathnames for reasons that I've got no control over. (I'm aware that this isn't normal practice.)

When I call

t开发者_运维技巧arobject.add("/foo/xx1", "/bar/xx1")

the arcname argument "/bar/xx1" is run through os.path.normpath() and converted to "bar/xx1"

How do I avoid this and end up with "/bar/xx1" as I require?

I've read that I can replace normpath somewhere, but I'm fairly new to Python and I'm not sure how to do this or what the wider implications would be.

edit

After looking at this question I had a closer look at the tarinfo object, and this seems to work:

my_tarinfo = tarobject.gettarinfo("/foo/xx1")
my_tarinfo.name = "/bar/xx1"
tarobject.addfile(my_tarinfo, file("/foo/xx1"))    

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You really do strange things. You need to copy /usr/lib64/python/tarfile.py to a directory in your PYTHONPATH. Then you can modify this file. But you need to bundle you own tarfile module with your code.