How to clone a Python generator object?
You can use itertools.tee():
walk, walk2 = itertools.tee(walk)
Note that this might "need significant extra storage", as the documentation points out.
If you know you are going to iterate through the whole generator for every usage, you will probably get the best performance by unrolling the generator to a list and using the list multiple times.
walk = list(os.walk('/home'))