import praw, requests, ctypes, random, os

def downloadImage(imageUrl, localFileName):
    response = requests.get(imageUrl)
    if response.status_code == 200:
        with open(localFileName, 'wb') as fo:
            for chunk in response.iter_content(4096):
                fo.write(chunk)

r = praw.Reddit(user_agent="Wallpaper downloader")
submissions = r.get_subreddit("wallpaper").get_top_from_month(limit=100)
subs = [s for s in submissions]
image = None

while True:
    choice = random.randint(1, 100)
    submission = subs[choice]
    if "imgur.com/" not in submission.url:
        continue
    if ".jpg" in submission.url:
        image = str("C:/Users/Augusto/Pictures/wallpapers/"+submission.url.replace("http://i.imgur.com/", ''))
        if not os.path.isfile(image):
            downloadImage(submission.url, image)
        break

SPI_SETDESKWALLPAPER = 20 # According to http://support.microsoft.com/default.aspx?scid=97142
ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER, 0, image, 0)