Python - Difference Between Windows SystemParametersInfoW vs SystemParametersInfoA Function

Question

I have a quick question that I cannot seem to clarify, despite my research on Stack Overflow and beyond. My questions involves the Windows SystemParametersInfo function with

Answer 1

Internally, Windows uses Unicode. The SystemParametersInfoA function converts ANSI parameter strings to Unicode and internally calls SystemParametersInfoW. You can call either from Python whether 32- or 64-bit, in Python 2.x or 3.x. Usually you want the W version to pass and retrieve Unicode strings since Windows is internally Unicode. The A version can lose information.

Example that works in Python 2 or 3, 32- or 64-bit. Note that the W version returns a Unicode string in the buffer, while the A version returns a byte string.

from __future__ import print_function
from ctypes import *
import sys

print(sys.version)
SPI_GETDESKWALLPAPER = 0x0073
dll = WinDLL('user32')
buf = create_string_buffer(200)
ubuf = create_unicode_buffer(200)
if dll.SystemParametersInfoA(SPI_GETDESKWALLPAPER,200,buf,0):
    print(buf.value)
if dll.SystemParametersInfoW(SPI_GETDESKWALLPAPER,200,ubuf,0):
    print(ubuf.value)

Output (Python 2.X 32-bit and Python 3.X 64-bit):

C:\>py -2 test.py
2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:42:59) [MSC v.1500 32 bit (Intel)]
c:\windows\web\wallpaper\theme1\img1.jpg
c:\windows\web\wallpaper\theme1\img1.jpg

C:\>py -3 test.py
3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) [MSC v.1900 64 bit (AMD64)]
b'c:\\windows\\web\\wallpaper\\theme1\\img1.jpg'
c:\windows\web\wallpaper\theme1\img1.jpg

Answer 2

On Windows 3.x/95/98/ME it is likely that only SystemParametersInfoA works correctly. On all other systems both the A and W flavor will work regardless of the OS bitness.

Assuming you only support "recent" versions of Windows, you should just pick the flavor most comfortable for you to use in your language and that usually means the flavor that matches the default string type in your language.

If you want to support both Python v2 & v3 you would have to choose at run-time which function to call if you are using the default string type.