text: #!/usr/bin/python
  
  '''Uses Cocoa classes via PyObjC to set a random desktop picture on all screens.
  Tested on Mountain Lion and Mavericks.
  
  See:
  https://developer.apple.com/library/mac/documentation/cocoa/reference/applicationkit/classes/NSWorkspace_Class/Reference/Reference.html
  
  https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSURL_Class/Reference/Reference.html
  
  https://developer.apple.com/library/mac/documentation/cocoa/reference/applicationkit/classes/NSScreen_Class/Reference/Reference.html
  '''
  import glob
  import random
  
  from AppKit import NSWorkspace, NSScreen
  from Foundation import NSURL
  
  pictures_glob = glob.glob("/Library/Desktop Pictures/*.jpg")
  picture_path = random.choice(pictures_glob)
  
  # generate a fileURL for the desktop picture
  file_url = NSURL.fileURLWithPath_(picture_path)
  
  # make image options dictionary
  # we just make an empty one because the defaults are fine
  options = {}
  
  # get shared workspace
  ws = NSWorkspace.sharedWorkspace()
  
  # iterate over all screens
  for screen in NSScreen.screens():
      # tell the workspace to set the desktop picture
      (result, error) = ws.setDesktopImageURL_forScreen_options_error_(
                  file_url, screen, options, None)