Creating a background changer in python with ctypes, not working

Question

I'm working on a simple (I thought) program to set a different desktop background for every day of the week. It runs with no errors but nothing happens. The path to the images are valid. Any ideas?

import time;
import ctypes;
SPI_SETDESKWALLPAPER = 20

localtime = time.localtime(time.time())
wkd = localtime[6]

if wkd == 6:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\1.jpg",0)

elif wkd == 0:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\2.jpg",0)

elif wkd == 1:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\3.jpg",0)

elif wkd == 2:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\4.jpg",0)

elif wkd == 3:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\5.jpg",0)

elif wkd == 4:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\6.jpg",0)

elif wkd == 5:
    ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER,0,r"C:\Users\Owner\Documents\Wallpaper\7.jpg",0)

A day is a long time to wait to check code. Try running it as a loop so it calls `ctypes.windll.user32.SystemParametersInfoA` every couple of seconds and see if anything happens, or if it changes the background. — , Feb 12 '14 at 00:12
Nothing is returned in the DOS shell, if that's what you mean. — user3299467, Feb 12 '14 at 00:13
@user3299467: No, I mean the return value of the function call. — Dolda2000, Feb 12 '14 at 00:14
@Lego That wouldn't significantly effect system resources would it? — user3299467, Feb 12 '14 at 00:14
Try `print(ctypes.windll.user32.SystemParametersInfoA(...))`. — Dolda2000, Feb 12 '14 at 00:15
You need to use `fWinIni=SPIF_SENDCHANGE`, which is 2. This broadcasts a `WM_SETTINGCHANGE` message. — Eryk Sun, Feb 12 '14 at 00:16
@user3299467: The same as is currently there. Just modify the whole statements with a `print` around them. — Dolda2000, Feb 12 '14 at 00:19
Just make the last argument `2` instead of `0`. Read the [docs](http://msdn.microsoft.com/en-us/library/ms724947). — Eryk Sun, Feb 12 '14 at 00:19
@user3299467: The [docs](http://msdn.microsoft.com/en-us/library/ms724947) will tell you that that means there was an error in the function, and gives the example that it may be that the file wasn't found. Are you sure your paths are correct? Unfortunately, there doesn't seem to be a way to get a more exact error specification. — Dolda2000, Feb 12 '14 at 00:23
Pretty sure yeah. There may be an error in the formatting, but the paths themselves are correct. — user3299467, Feb 12 '14 at 00:26
Just to be on the safe side, try so that the Python program can actually open the files. Add an `open(r"C:\Users\Owner\Documents\Wallpaper\1.jpg")` somewhere in the program and check so that it doesn't give any errors. — Dolda2000, Feb 12 '14 at 00:28
Interesting, that didn't work. No errors though. I tried not doing the path and just doing open("1.jpg") and that didn't go through either. (They are in the same folder) — user3299467, Feb 12 '14 at 00:31
I did the print thing and got "<_io.TextIOWrapper name='C:\\Users\\Owner\\Documents\\Wallpaper\\1.jpg' mode='r' encoding='cp1252'>" back, if that helps. — user3299467, Feb 12 '14 at 00:35
You're using Python 3.x. It's passing a unicode (UTF-16) string. Use `SystemParametersInfoW` to pass a wide string. — Eryk Sun, Feb 12 '14 at 00:35
Also, Lego was saying I was waiting too long to check code. I was putting it in Autostart And using Task Scheduler at midnight so it wouldn't have to run all the time. Would it be better if I had it run on a loop? — user3299467, Feb 12 '14 at 00:44

score 4 · Answer 1 · edited Jan 16 '20 at 16:58

I must have read every existing site on this topic and just before giving up, came to this working code (win7 pro 64 bit, python 3.4)

import ctypes
SPI_SETDESKWALLPAPER = 0x14     #which command (20)

SPIF_UPDATEINIFILE   = 0x2 #forces instant update
src = r"D:\Downloads\_wallpapers\3D-graphics_Line_025147_.jpg" #full file location
#in python 3.4 you have to add 'r' before "path\img.jpg"

print(ctypes.windll.user32.SystemParametersInfoW(SPI_SETDESKWALLPAPER, 0, src, SPIF_UPDATEINIFILE))

It uses SystemParametersInfoW instead of SystemParametersInfoA (W instead of A).

Hope it helps you and many others who seem to have similar problems.

score 2 · Answer 2 · answered Dec 31 '16 at 07:10

If you are using Python 3 you should use ctypes.windll.user32.SystemParametersInfoW instead of ctypes.windll.user32.SystemParametersInfoA(W instead of A as this answer said). Another answer described that because in Python 3 the str type is in form of UTF-16 as wchar_t * in C.

What's more, please minimize the code like this:

import time;
import ctypes;
SPI_SETDESKWALLPAPER = 20

wallpapers = r"C:\Users\Owner\Documents\Wallpaper\%d.jpg"

localtime = time.localtime(time.time())
wkd = localtime[6]
ctypes.windll.user32.SystemParametersInfoW(SPI_SETDESKWALLPAPER, 0, wallpapers%(wkd+1), 0)

Don't Repeat Yourself.

score 1 · Answer 3 · answered Feb 12 '14 at 00:21

This is not an answer to your question, but you can generally minify your program and remove redundancy by doing something like this instead:

import time;
import ctypes;
SPI_SETDESKWALLPAPER = 20

wallpapers = [
    r"C:\Users\Owner\Documents\Wallpaper\1.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\2.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\3.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\4.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\5.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\6.jpg",
    r"C:\Users\Owner\Documents\Wallpaper\7.jpg",
]

localtime = time.localtime(time.time())
wkd = localtime[6]
ctypes.windll.user32.SystemParametersInfoA(SPI_SETDESKWALLPAPER, 0, wallpapers[wkd], 0)

score 0 · Answer 4 · edited Apr 10 '22 at 13:21

I discovered a really weird reason on why my code wasn't working.

I had the function like this:

ctypes.windll.user32.SystemParametersInfoW(0x14, 0, """C:/Users/myUser/Desktop/
VSCoding/Python/TheWelcomer/test.jpg""", 0x2)

(There was an enter between the path)

and that didn't work, I just got a black desktop background

But when I got rid of that enter, like this:

ctypes.windll.user32.SystemParametersInfoW(0x14, 0, """C:/Users/myUser/Desktop/VSCoding/Python/TheWelcomer/test.jpg""", 0x2)

it worked

Creating a background changer in python with ctypes, not working

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