Detect OS dark mode in Python

Question

I'm writing a small program in python with a GUI that I'm using tkinter for. What I'd like to do is add dark mode support to my program. Mac OS, Ubuntu (at least Gnome) and Windows 10 all have a system-wide setting for "dark mode" that'll make all programs automatically run with a dark theme.

But how do I check that settings (ideally, OS-independant) so my program knows if it needs to render light mode or dark mode? I found a bunch of libraries like darkdetect that'll handle this for MacOS, but I haven't found anything for Ubuntu and Windows 10.

I know that I can use stuff like ttkthemes to create a dark themed design for my program, but how do I know when to enable that? How can a python script running on Windows 10 or on Ubuntu 20.04 figure out if the user enabled the dark mode in the operating system settings?

Ideally I'm looking for a solution / code that'll work on all three operating systems, but if that's not possible (as I suspect) OS-dependant code would be fine as well. I just can't find proper examples for non-MacOS systems anywhere.

Answer 1

Quick answer for Windows 10

def detect_darkmode_in_windows(): 
    try:
        import winreg
    except ImportError:
        return False
    registry = winreg.ConnectRegistry(None, winreg.HKEY_CURRENT_USER)
    reg_keypath = r'SOFTWARE\Microsoft\Windows\CurrentVersion\Themes\Personalize'
    try:
        reg_key = winreg.OpenKey(registry, reg_keypath)
    except FileNotFoundError:
        return False

    for i in range(1024):
        try:
            value_name, value, _ = winreg.EnumValue(reg_key, i)
            if value_name == 'AppsUseLightTheme':
                return value == 0
        except OSError:
            break
    return False

• It checks if winreg can be imported, if not you are probably not using Windows
• The relevant registry key is searched, if not found, it is assumed that dark mode is not enabled
• If the registry key is present and the value is set to 0, dark mode is set