rotate_desktop_background.py

#!/usr/bin/env python

"""
Desktop Background Rotater

Background images:
    http://bitday.me

Crontab entry:
    # min  hr mday month wday command
      */15 *  *    *     *    /Users/pedram/Utils/rotate_desktop_background.py

Locale information:
    http://www.wolframalpha.com/input/?i=sunrise+in+austin
    http://www.wolframalpha.com/input/?i=sunset+in+austin
"""

import shlex
import datetime
import subprocess

CURRENT_BG = "/tmp/current_desktop_background.dat"
CHANGE_CMD = """/usr/bin/osascript -e 'tell application "Finder" to set desktop picture to POSIX file "%s/%s"'"""
BG_DIR     = "/Users/pedram/Pictures/Backgrounds/BitDay-2560x1600/"
BG_MAP     = \
[
    "_night.png",           # 0000
    "_late_night.png",      # 0300
    "_morning.png",         # 0600
    "_late_morning.png",    # 0900
    "_afternoon.png",       # 1200
    "_late_afternoon.png",  # 1500
    "_evening.png",         # 1800
    "_late_evening.png",    # 2100
]

########################################################################################################################
def launch_command (args, stdin=""):
    """
    Launch the specified command with args (each as a separate item of a list).
    """

    # if a list was not provided, encode the string in UTF-8 and convert to list.
    if type(args) is not list:
        args = shlex.split(args.encode("utf-8", "ignore"))

    process  = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = process.communicate(stdin)

    return out, err

########################################################################################################################
if __name__ == "__main__":

    # what's the current background set to?
    current_bg = ""

    with open(CURRENT_BG, "a+") as fh:
        current_bg = fh.read()

    # what time is it?
    now = datetime.datetime.now()

    # hours divided by 3 = index into our BG map table
    desired_bg = BG_MAP[now.hour/3]

    # if the desired and current don't match, set the background.
    if current_bg != desired_bg:
        launch_command(CHANGE_CMD % (BG_DIR, desired_bg))

        # update the current background on disk.
        with open(CURRENT_BG, "w+") as fh:
            fh.write(desired_bg)