os.walk restart

[Keir Vaughan-taylor]

I am traversing a large set of directories using

for root, dirs, files in os.walk(basedir):
    run program

Being a huge directory set the traversal is taking days to do a
traversal.
Sometimes it is the case there is a crash because of a programming
error.
As each directory is processed the name of the directory is written to
a file
I want to be able to restart the walk from the directory where it
crashed.

Is this possible?