synching with os.walk()

petercable at petercable at
Mon Nov 27 10:46:37 CET 2006

On Nov 24, 7:57 am, "Andre Meyer" <m... at> wrote:
> os.walk() is a nice generator for performing actions on all files in a
> directory and subdirectories. However, how can one use os.walk() for walking
> through two hierarchies at once? I want to synchronise two directories (just
> backup for now), but cannot see how I can traverse a second one. I do this
> now with os.listdir() recursively, which works fine, but I am afraid that
> recursion can become inefficient for large hierarchies.

I wrote a script to perform this function using the dircmp class in the
filecmp module. I did something similar to this:
import filecmp, os, shutil

def backup(d1,d2):
  print 'backing up %s to %s' % (d1,d2)
  compare = filecmp.dircmp(d1,d2)
  for item in compare.left_only:
    fullpath = os.path.join(d1, item)
    if os.path.isdir(fullpath):
    elif os.path.isfile(fullpath):
  for item in compare.diff_files:
  for item in compare.common_dirs:

if __name__ == '__main__':
  import sys
  if len(sys.argv) == 3:
    backup(sys.argv[1], sys.argv[2])

My script has some error checking and keeps up to 5 previous versions
of a changed file. I find it very efficient, even with recursion, as it
only actually copies those files that have changed. I sync somewhere
around 5 GB worth of files nightly across the network and I haven't had
any trouble.

Of course, if I just had rsync available, I would use that.

Hope this helps,


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