Query Windows 10/8 Monitor Scaling from Python Script?

I have written an application in python 3.6 and would like to run a command to see what the current scaling for a monitor is in Windows 10 or 8 - something like how the following returns screen resolution:

user32 = ctypes.windll.user32
screensize_l = user32.GetSystemMetrics(0)
screensize_w = user32.GetSystemMetrics(1)

I understand that the easiest way to do this may be to make my application DPI aware, but doing so causes lots of additional problems in my application - so I would like to avoid this option.

I have looked in the windows documentation and thought "GetDpiForMonitor" or "GetScaleFactorForMonitor" may be what I am looking for, but don't know how to implement these commands.

I already use both win32api and ctypes so anything relying on either of these would be fine - any help would be greatly appreciated!

Solution

On Windows 10, the following code (you need pywin32):

import ctypes
import win32api

PROCESS_PER_MONITOR_DPI_AWARE = 2
MDT_EFFECTIVE_DPI = 0

def print_dpi():
    shcore = ctypes.windll.shcore
    monitors = win32api.EnumDisplayMonitors()
    hresult = shcore.SetProcessDpiAwareness(PROCESS_PER_MONITOR_DPI_AWARE)
    assert hresult == 0
    dpiX = ctypes.c_uint()
    dpiY = ctypes.c_uint()
    for i, monitor in enumerate(monitors):
        shcore.GetDpiForMonitor(
            monitor[0].handle,
            MDT_EFFECTIVE_DPI,
            ctypes.byref(dpiX),
            ctypes.byref(dpiY)
        )
        print(
            f"Monitor {i} (hmonitor: {monitor[0]}) = dpiX: {dpiX.value}, dpiY: {dpiY.value}"
        )


if __name__ == "__main__":
    print_dpi()

gives the following output on my machine with 3 monitors and 1 scaled to 125%:

Monitor 0 (hmonitor: <PyHANDLE:65539>) = dpiX: 96, dpiY: 96
Monitor 1 (hmonitor: <PyHANDLE:65537>) = dpiX: 120, dpiY: 120
Monitor 2 (hmonitor: <PyHANDLE:65541>) = dpiX: 96, dpiY: 96

If you do not want to set your own application as a dpi-aware per monitor, you could try launching some variant of the above code in another process using the multiprocessing module and retrieve the results.

hope this helps.