background script to password protect wallpaper changing in Ubuntu 14.04

password_wallpaper.py

#!/usr/bin/env python3

"""
Copyright (C) 2014 Jacob Vlijm
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or any later version. This
program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details. You
should have received a copy of the GNU General Public License along with this
program. If not, see <http://www.gnu.org/licenses/>.
"""

import time
import subprocess

set_password = "monkey"

key = "org.gnome.desktop.background picture-uri "
read = "gsettings get "+key; change = "gsettings set "+key
set_wallpaper = subprocess.check_output(["/bin/bash", "-c", read]).decode("utf-8").strip()
pass_window ='zenity --entry --entry-text="Enter password" --text="Enter password" --title="password" --hide-text'

def check_wall():
    global set_wallpaper
    curr_wallpaper = subprocess.check_output(["/bin/bash", "-c", read]).decode("utf-8").strip()
    if curr_wallpaper != set_wallpaper:
        subprocess.Popen(["/bin/bash", "-c", change+set_wallpaper])
        try:
            entered_password = subprocess.check_output(
                ["/bin/bash", "-c", pass_window]).decode("utf-8").strip()
        except Exception:
            entered_password = None
        if entered_password == set_password:
            subprocess.Popen(["/bin/bash", "-c", change+curr_wallpaper])
            set_wallpaper = curr_wallpaper
    else:
        pass

while True:
    check_wall()
    time.sleep(3)

Mild password protection, meant for home use.
explantion: http://askubuntu.com/a/533537/72216