def flipwritable ( fn , mode = None ) : if os . access ( fn , os . W_OK ) : return None old_mode = os . stat ( fn ) . st_mode os . chmod ( fn , stat . S_IWRITE | old_mode ) return old_mode
python change file to readonly
Flip the writability of a file and return the old mode . Returns None if the file is already writable .
def flipwritable(fn, mode=None):
    """
    Flip the writability of a file and return the old mode. Returns None
    if the file is already writable.
    """
    if os.access(fn, os.W_OK):
        return None
    old_mode = os.stat(fn).st_mode
    os.chmod(fn, stat.S_IWRITE | old_mode)
    return old_mode