permissions.py

#!/bin/env python2
#
#
##############################################################################
### NZBGET POST-PROCESSING SCRIPT                                          ###
# chmod for nzbget
# NOTE: This script requires Python to be installed on your system.
##############################################################################
### OPTIONS                                                       ###

### NZBGET POST-PROCESSING SCRIPT                                          ###
##############################################################################


import os
import stat
import sys

# Exit codes used by NZBGet
POSTPROCESS_SUCCESS=93
POSTPROCESS_ERROR=94
# Check if the script is called from nzbget 11.0 or later
if not 'NZBOP_SCRIPTDIR' in os.environ:
        print('*** NZBGet post-processing script ***')
        print('This script is supposed to be called from nzbget (11.0 or later).')
        sys.exit(POSTPROCESS_ERROR)

for dirname, dirnames, filenames in os.walk(os.environ['NZBPP_DIRECTORY']):
    st = os.stat(dirname)
    os.chmod(dirname, st.st_mode | stat.S_IRWXG | stat.S_IRWXO)
    print dirname
    for filename in filenames:
        st = os.stat(os.path.join(dirname, filename))
        os.chmod(os.path.join(dirname, filename), st.st_mode | stat.S_IRWXG | stat.S_IRWXO) 

# All OK, returning exit status 'POSTPROCESS_SUCCESS' (int <93>) to let NZBGet know
# that our script has successfully completed.
sys.exit(POSTPROCESS_SUCCESS)

Will this work on Windows to change file read only attribute?

If executed by a user that can do so, yes. However this script would be executed by nzbget, on files saved by nzbget.

Thanks, that is exactly what I need