Try to remove all comments from a file, and save it if changes were made.

def example_write_file_to_disk_if_changed():
    """ Try to remove all comments from a file, and save it if changes were made. """
    my_file = FileAsObj('/tmp/example_file.txt')
    my_file.rm(my_file.egrep('^#'))
    if my_file.changed:
        my_file.save()