Something

#!/usr/bin/env pythonimport osimport sysimport shutildef rename(root, name, replace):    src = os.path.join(root, name)    dest = os.path.join(root, name.replace(" ", replace))    if filename.find(" ") != -1:         try:                os.rename(src, dest)        except OSError:            print "%s: ERROR: Permission Denied: %s" % (sys.argv[0], src)            sys.exit(1)if __name__ == "__main__":    if len(sys.argv) != 3:        print "%s <dir> <replacement>" % (sys.argv[0])        sys.exit(1)    dir = os.path.abspath(sys.argv[1])    replace = sys.argv[2]    if not os.path.isdir(dir):        print "%s: The first argument needs to be a directory" % (sys.argv[0])    for dirpath, dirnames, filenames in os.walk(dir, topdown=False):         for filename in filenames:            rename(dirpath, filename, replace)        for dirname in dirnames:            rename(dirpath, dirname, replace)